# AR Fume Safety/Prevention/Treatment



## toadiesop (Jun 21, 2007)

The power of AR fumes as been on my mind for a while and something the new guy Scavenger said inspired me to make this thread.

We've all heard the stories that Scavenger just stated "Breathe fumes, die two weeks later"

AND IN NO WAY AM I DOWNPLAYING THE DANGERS WITH AR OR ANY OTHER CHEMICALS USED IN REFINING!!!

But, seriously, how much do you have to breathe before "the fear" sets in. I haven't used AR yet and when I do it will be outside, well ventilated, you know the drill.

I'm just wondering if these stories are a little exaggerated and if some of the pros could explain a little more on fume inhalation. I'm thinking accidents and what not. I mean 

Now obviously you wouldn't want to stick your head right in the BFRC and breathe in like you would on the first day of spring, but if by chance you get a little wiff, how serious is it?

What should you do if it happens? And on what scale? How much would you have to inhale before you should take action (if you don't die on the spot?)

What are some symptoms that something is wrong? Nausea? Vomiting? Shakes? Blurry Vision? That whole death thing?

We all know the dangers and like I said, I'm not downplaying the seriousness of the fumes but I guess this "what to do IF" thread.

It's all well and good to display the dangers everywhere but I think we need more posts on what to do if an accident happens.

Take it away guys.


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## toadiesop (Jun 21, 2007)

I should also state that information on batch size would be helpful too. 

Obviously if your doing 5 pounds of material at a time in 5 gallon buckets you need a respirator and you need to be far, far away from any and all living creatures.

What about in the refining stage? Just a little bit of AR in pyrex dealing with 5 grams or so of mud, or foils, or karat scrap?

What are the fumes like on a small scale like that?

Is just being in an open area outside with a good wind and some common sense enough?


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## lazersteve (Jun 21, 2007)

Toadie,

For starters here's a link to a short NO2 MSDS:

NO2 Short MSDS

and another to a long NO2 MSDS:

NO2 Long MSDS

and when using AR you'll have Chlorine gas also.

Remember that when you dissolve metals with AR or Nitric acid that 25-50% of the acid becomes this gas. Here's the post where GSP did the math for the Nitirc Acid required in the reaction:

Nitric Acid Reaction for 1 pound of copper

In a nutshell he states you need 1/2 gallon of 70% HNO3 to dissolve 1 pound of copper and in that reaction you should expect 50% of the acid (1/4 gallon) to become the deadly gas NO2 when used in concentrated form. He also states this is valid information for the AR reaction.

As you can see, the potential hazard is real when working with a single pound of scrap pins. Of course as the batches get smaller so does the cloud.

I've personnally processed a 10# batch of cpus and fingers using Poor Man's AR and the BFRC lasted no less than 3 hours. I did this outdoors and was very concerned for my pets and myself.

Catfish uses smaller batches of AR very frequently and can give us more information on these sized batches. GSP and Harold have obviously a vast amount of experience in this area and hopefully will fill in the blanks I have left. Many other members can provide stories of their experiences as well.

Steve


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## toadiesop (Jun 22, 2007)

Thanks for the links Steve.

And a 3 hour BFRC??? Wow, sounds like a nightmare! :shock: 

I've seen pictures of 5# of scrap in Poor Man's AR from a CD I bought on ebay last summer. That's how my minds eye sees the AR process. There was a large amounts of fumes.

I'll see if I can find that CD and maybe post a couple of pictures from it. It might even say who made it. no-reserve perhaps?


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## toadiesop (Jun 22, 2007)

> Copyright 2003, Noble Metals Recovery, Steve Spevak.



That's no_reserve correct?

He just posted here tonight too. That is if "Nobel Metals Recovery, LL" is him.


And my mistake. It was a 9# batch.


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## lazersteve (Jun 22, 2007)

Toadie,

I have a copy of the cd also. No_reserve is Steve aka Noble Metals Recovery LL here on the forum. He's a really great guy and very willing to help. You should ask him to post some of his photos of the process. :wink: 

Steve


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## Noxx (Jun 22, 2007)

Yes, I bought the CD from him too. When I did it, I never taught I would create a gold refining forum two years later


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## toadiesop (Jun 22, 2007)

HAHAHAHAAA!! That's how it goes Noxx. I can't believe I didn't beat you to it! :lol: 

So Steve, any information on those fumes would be greatly appreciated. 

And I'm sure more people can chime in on this question.

When you are dealing with 5 gallon bucket sized batches do you just stay away until it's done, or can you walk up and stir it without a respirator if you are upwind?


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## lazersteve (Jun 22, 2007)

Toadie,

You missed my reply about fumes... scroll up and see. The fumes info is in the same posts as the story about the 10# of scrap.

Steve


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## toadiesop (Jun 22, 2007)

No, I read it Steve. I guess I'm being a little to wordy. I'm like like sometimes  my brain doesn't shut off and I just type my thoughts as quickly as they hit me.

I guess I'll do it like this.

1. When you have the BFRC how far away should you be without a respirator on and be safe to breathe normally? Do the fumes dissipate within a certain radius or are you still in harms way if you're, say 20 feet away.

2. Can you get up to the bucket using common sense? (wind direction, holding your breath, ect)

3. How do you know when it's safe?

4. How do you know when you're too close, or in trouble? The smells? Does your nose burn? Will you get light headed? I guess this is the main question I have. How do you know somethings wrong?

5. If that happens, what do you do?


I'm by no means a chemist, but I'm learning. 8)


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## goldsilverpro (Jun 22, 2007)

I just discovered a terrific patent that could revolutionize this whole NO2 problem. I don't have it in front of me but I'll find the patent # tomorrow. Also, it would need some study and some math and lab work to make it usable.

It basically consists of adding definite quantities of strong H2O2 to any dissolving solution containing nitric acid. This would include nitric alone, AR, or NaNO3 + HCl. According to the patent, the H2O2 converts the NO that is produced back to HNO3 - in the solution itself! In this system, *ZERO* NO2 brown fumes are given off. The HNO3 is, therefore, twice as efficient and the presence of the H2O2 speeds up the reaction. Killer Patent! Three birds with one stone - No brown fumes - Acid will dissolve twice as much metal - Faster reaction.

To prevent the H2O2 from decomposing too rapidly, a small amount of ethylene glycol (antifreeze) is used as a preservative. The common 3% H2O2 won't work. Stronger stuff is needed.

There's a similar patent that uses sulfamic acid, I think, for the same purpose.

I've mentioned before that a guy I knew used H2O2 in a multi-stage NO2 scrubber. The H2O2 converted the NO2 to HNO3 in the 1st stage. The 2nd stage neutralized the HNO3 with NaOH. In Aflac's discussion of the machine he promotes, he said the scrubbers worked the same way, although he wouldn't say what the scrubber solutions were.

All of this goes hand in hand. That's why I was excited when I saw that patent.

I just found the Patent #'s. 3945865 and 3367874. There are probably more out there.

I just found these and haven't really studied them yet.

Steve, let me know what you think.


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## lazersteve (Jun 22, 2007)

Toadie, 

I really don't want to advocate bypassing *proper* safety procedures when working with deadly gases, but I don't want to leave you hanging on the answers so here's my stab at your questions:

[img::]http://www.goldrecovery.us/images/skullnbones_smallrev.jpg[/img]
1) The bulk of the cloud remains over the bucket in a cone shape that is big at the top and the size of the mouth of the bucket at the bottom. Of course the wind and temperature is going to influence this. The cloud will stay low to the ground when it's colder. The main concentration of the fumes is in the red portion, but *not all of the fumes are visible*.

2) I did the reaction outside on a average spring day. I held my breath the one time I got within 15 feet of the bucket when the cloud was present (to cover the bucket with an inverted plastic garbage can). I keep my face away from the bucket. I tried not to breath at all until I was at least 20 feet away. I wore gloves and tight goggles at all times.

3) I let the bucket sit for a full hour AFTER the cloud stopped. Even then I used extreme caution when approaching.

4) The first signs of exposure is a tickeling feeling in the nose or throat. The odor is bleachlike. If you breath any you will begin coughing, this is bad.

5) Read the MSDS for exposure treatments before you begin. Be prepared with these countermeasures on hand in the event of an emergency. 

[img::]http://www.goldrecovery.us/images/skullnbones_smallrev.jpg[/img]

Again, I *do not* advise you to perform large scale reactions using AR without all the PROPER safety equipment (Respirator, Tight Goggles, and Chemical Gloves). Even if you are safe, your neighbors and pets may not be!

Stay safe Toadie,

Steve


P.S. This is my 1000th Post !!!!!!


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## Noxx (Jun 22, 2007)

GSP, this patent is VERY interesting. I will read it.

Steve, I congrats for your 1000th post. Just look under your name


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## goldsilverpro (Jun 22, 2007)

FUME HOOD! FUME HOOD! FUME HOOD! FUME HOOD!


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## lazersteve (Jun 22, 2007)

GSP,

I seem to remember seeing these patents late one night while googling. I had forgotten all about them until you mentioned them. I've only read the abstracts and will need time to study them. 

If this pans out then it will make life a lot better and safer for the AR crowd.

Great post as usual GSP!

Steve


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## Harold_V (Jun 22, 2007)

goldsilverpro said:


> FUME HOOD! FUME HOOD! FUME HOOD! FUME HOOD!



Where have I heard that before?

Harold


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## toadiesop (Jun 22, 2007)

Thanks guys!

And Steve, I guess my motives for this thread were twofold.

For myself I wanted to know what it would be like in small batches. I don't think I'll ever be comfortable doing HUGE batches of AR and I don't see a time I'll ever need to. AP works just fine! I was thinking about when I have an ounce or so of buttons saved up and I want to hit 3 nines. Just a little bit of AR in a measuring cup. 

Like you said, no all fumes are visible and that was one of my concerns.


The other reason I asked is because, while I know about staying safe and asking questions many of the other new people might not. It's good to know layman's specifics sometimes like "Stay 20 feet away" "Wait an hour after the fumes die down" ect.

And also how to tell that something in wrong and what to do.

Thanks everyone!


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## lazersteve (Jun 22, 2007)

Harold said:


> goldsilverpro wrote:
> FUME HOOD! FUME HOOD! FUME HOOD! FUME HOOD!
> 
> 
> Where have I heard that before?



I know, I know, I know... I'm working more on that problem this weekend. After the garage is completely reorganized, I'll layout some plans and share them with everyone. 

All,

As the pros have so graciously pointed out time and time again, there is *NO SUBSTITUTE* for a good fume hood where safety is concerned when dealing with toxic gases. I whole heartedly agree with them and would recommend that everyone here work towards building one. My previous post about 'backyard AR' was a *very scary* experience to say the least. I was very lucky to come thru it safely. As I stated in that post, just because you take all the safety precautions for yourself, it DOESN'T mean those around you will be safe. 

My new mantra until mine is completed:

FUME HOOD! FUME HOOD! FUME HOOD! FUME HOOD! 8) 

Be safe and take care,


Steve


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## Anonymous (Jun 24, 2007)

:idea: This works great for 14 pound pentium chip batches... 
using a 3/4 gallon poor or rich man's 'recipe'.

Using the lid from the 5 gallon drywall bucket, REMOVE RUBBER GASKET from inside the lid's edge, drill or carve hole for PVC pipe with elbows, to allow the pipe to angle downward into a plastic 24" deep bin 3/4 way full of water and wood ash mix, just gotta mix it up so it's like a THIN milkshake consistency since the fumes will come out of the pipe at pressure, you want the bubbles to travel freely from the end of that pipe, not clog like will happen as the ash settles, LOL, but anyways, you get the picture... You could try something liquid like premixed water and drano. Either way, an alkaline solution with the pipe near the bottom cuts the fumes down about 95%. Cover the bin with a wet towel and sprinkle the ash on top of that, might need some clamps to hold the towel in place. This traps/neutralizes the fumes that escape the alkaline liquid part. As with all reactions, when the bin bubbling stops, the reaction is nearing the end. Take the pipe out soon, as the reaction cools, it will suck up the water through the pipe and a possible nasty surprise could ensue. You'll notice that some fumes will stay in the bucket, as you remove the lid, hold your breath. The liquid on the underside of the lid is highly corrosive and should be rinsed into that bin. I use a quart or so of rain water. You'll also want to rinse down the inside of the bucket as the condensed liquid is highly corrosive. 

There are some other methods that are FREE and work great too, I'll post them later. I think small batches are for the birds! LOL It is safe to say that I do this all without gloves or respirators.

some conditions affecting fumes: Humidity, wind direction/speed, air temp, etc... all true. If humid, use the neutralizer. If dry air and windy, just let it rip, using the lid with a vent hole a good 1000 feet from neighbors, wildlife, etc. Make sure the hole in lid is clear first though. You can also cover that with a cloth/ash to minimize the escape. As long as you don't seal the vent shut, you'll be OK. I've even trapped the fumes, cooled them into liquid then used them to dissolve more gold plated stuff. Either way, fumes are nasty, stay upwind and try to minimize them if possible. The garbage can upside down seems a bit archaic, but, to each their own, :lol: 

AF 8)


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## goldsilverpro (Jun 24, 2007)

I couldn't follow you 100% but, I get the idea that what you have is excellent. A few photos would be great.


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## Anonymous (Jun 25, 2007)

This might sound crazy but I had an idea on how to control fumes. Can you use a shop vac with some sort of medium as a "filter " to takt the fumes out of your cell? Possibly connect the hose to a homemade "hood". And if this is possiblte what would you use as a filter "medium"?

Any help on this would be appreciated sine this is the concept I was thing of using in my* first* cell setup


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## Noxx (Jun 27, 2007)

GSP, could you tell what is the minimum concentration of H202 can be used ? I don't think 3% would work...
Thanks


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## goldsilverpro (Jun 27, 2007)

I still haven't gone over the patent, Noxx. I would think that the best is 30% (100 volume) or 35% (120 volume).


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## Noxx (Jun 27, 2007)

It's not possible to obtain that in common stores right ?


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## goldsilverpro (Jun 27, 2007)

I seem to remember seeing it on a list of common sources. I have since tried to find this with no luck.


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## aflacglobal (Jun 27, 2007)

Chris,

You been in this awhile and know these things. Check out my post on Triatomic oxygen and see what you think. ?????
http://goldrefiningforum.com/phpBB3/viewtopic.php?t=628

Any Ideas ?

Ralph


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## lazersteve (Jun 27, 2007)

GSP said:


> I seem to remember seeing it on a list of common sources. I have since tried to find this with no luck.



Here's the topic I think you may be after:

Common Chemicals

Steve


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## austexjwlry (Jun 28, 2007)

Toadisop

AR fumes are real sneaky. At first with mild poisoning you'll have an overall sense of not well being, slight headache, slight stomach ache with loss of appetite, slightly blurred vision, slightly labored breathing.

I read somewhere that some of the AR fumes can bond almost instantly with organic materials like our skin! 

With severe poisoning your eyes will leak as when crying, you'll sweat profusely, you'll drool excessively, you'll have to urinate repeatedly, you'll vomit repeatedly. You'll be really light headed and disoriented. Your body will use every way it has to try and remove the toxins from your system! You'll become very weak from lack of oxygen etc. I truly almost died, no exaggeration at all! Sorry to so graphic.

Respect these fumes! There are no acceptable amounts to breathe!
The one thing you can't buy is experience; please listen to these guys. You don't want to experience this form of poisoning.

Wayne


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## Noxx (Jun 28, 2007)

I'm sorry to hear that...

Protect yourself ! Use a full face shield and a fume hood ! <== Strict minimum !


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## goldsilverpro (Jun 28, 2007)

austex,

During my 40 years of refining, I worked with near boiling aqua regia, often in very large quantities, at least 1 out of every 3 days on the average. I've NEVER experienced any of the symptoms that you mentioned, even those you list for mild exposure. Of course, from day one, I have always had a fume hood. However, even with a fume hood, there are often some AR smells from containers sitting around and from handling solutions. I seem to have developed a 6th sense of when to breathe, when not to breathe, and when to get the hell out of the area. It became automatic. I got very good at holding my breath.

I'm not trying to reduce the dangers and you're absolutely right in your warnings.


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## goldsilverpro (Jun 28, 2007)

Ralph,

I read all the stuff on ozone with interest. About my only experience is when I smell it around a busy copy machine. I can see possible applications in speeding up reactions and in waste disposal. It would be interesting to play with an ozone generator.


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## scavenger (Jun 28, 2007)

I'm on my second batch of AR (just a small amount) and I was thinking of doing the next small one in a beaker contained within a 25 liter plastic home brew barrel fitted with a water filled air lock. Is this a good idea? Or would the pressure build up be to great?


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## Noxx (Jun 28, 2007)

Pressure will certainly build up. When dissolving with AR or nitric acid, NOx gases are produced. They are very corrosive. I strongly recommend you to do it outside or in a fume hood.


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## Destroyer (Jul 8, 2007)

toadiesop said:


> No, I read it Steve. I guess I'm being a little to wordy. I'm like like sometimes  my brain doesn't shut off and I just type my thoughts as quickly as they hit me.
> 
> I guess I'll do it like this.
> 
> ...



I used to work on a Platform with H2S gas we put on an SCBA before we did anything. It should be the same here if you smell it it is too late you have been exposed I suggest a full facr MSA mask. H2S some people would try to test with the nose but at certain levels it kills the sense of smell, so you would never know it was there at all.


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## aflacglobal (Jul 9, 2007)

Ralph, 
I read all the stuff on ozone with interest. About my only experience is when I smell it around a busy copy machine. I can see possible applications in speeding up reactions and in waste disposal. It would be interesting to play with an ozone generator.

I have been studying it's effects without air pressure. In the atmosphere.
I am also on the trail of ozone in S.C.W.O. 
If it is dissolved in the water at low temp and then compressed to 3200 psi and about 700 degs then will it come out of the solution ( I think ). The amount that water can hold decreases with pressure and temp. Well if it's in solution and suddenly compressed and heated will it stay or go. 

If i goes , i imagine it would do some serious damage to any metals that happened to find themselves in the vicinity of that stream. Water acts funny at this point. lol Your the physicist.

Ralph


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## Noxx (Jul 17, 2007)

Do 35% hydrogen peroxyde can work with the patent technique ?
Thanks


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## aflacglobal (Jul 17, 2007)

Do 35% hydrogen peroxyde can work with the patent technique ? 
Thanks

What was you refering to ?


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## Noxx (Jul 17, 2007)

With the patent for NOx fumes... You can add Hydrogen Peroxide to stop NO2 fumes coming out of the solution and redissolving as nitric acid.


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## goldsilverpro (Jul 17, 2007)

I was the one that gave the patent number on that, Noxx. I skimmed it when I first saw it but, I seem to have forgotten about it. I'm not sure but, I think the amounts in the patent are based on using 35% H2O2. I'll try to remember to dig it out and look at it more carefully.

Patent #'s 3945865 and 3367874


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## Noxx (Jul 17, 2007)

Yes I do have the patent numbers but I can't understand how much I must use.

Thanks GSP


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## austexjwlry (Feb 18, 2008)

Ouch,,

If anyone has to go to the emergency room like my wife did on Jan. 17 this year with severe asthma like symptoms and running a fever. If your lungs are irritated and inflamed think twice about allowing them to treat you with a cortisone i.v. being pumped into your system to reduce inflamation as it can cause pulmonary edema, where your lungs start to fill up with your own fluids much like drowning. She reacted very badly to it. I almost lost her, 4 days in the hospital and well over $20,000. later she was able to come home. Respect these and all the fumes we produce!

You can buy quite a few fume hoods for the price of one emergency room visit! And no amount of money can replace a loved one!

Wayne


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## ddrew (Feb 22, 2008)

AquaFortis said:


> :idea: This works great for 14 pound pentium chip batches...
> using a 3/4 gallon poor or rich man's 'recipe'.
> 
> Using the lid from the 5 gallon drywall bucket, REMOVE RUBBER GASKET from inside the lid's edge, drill or carve hole for PVC pipe with elbows, to allow the pipe to angle downward into a plastic 24" deep bin 3/4 way full of water and wood ash mix, just gotta mix it up so it's like a THIN milkshake consistency since the fumes will come out of the pipe at pressure, you want the bubbles to travel freely from the end of that pipe, not clog like will happen as the ash settles, LOL, but anyways, you get the picture... You could try something liquid like premixed water and drano. Either way, an alkaline solution with the pipe near the bottom cuts the fumes down about 95%. Cover the bin with a wet towel and sprinkle the ash on top of that, might need some clamps to hold the towel in place. This traps/neutralizes the fumes that escape the alkaline liquid part. As with all reactions, when the bin bubbling stops, the reaction is nearing the end. Take the pipe out soon, as the reaction cools, it will suck up the water through the pipe and a possible nasty surprise could ensue. You'll notice that some fumes will stay in the bucket, as you remove the lid, hold your breath. The liquid on the underside of the lid is highly corrosive and should be rinsed into that bin. I use a quart or so of rain water. You'll also want to rinse down the inside of the bucket as the condensed liquid is highly corrosive.
> ...



I read this post with interest, and saw nothing to dispute it, or confirm it. Can anyone validate whether this is an effective method to use INSTEAD of a fume hood? If so, is this an accepted practice? 

AquaFortis, you mentioned '... some other methods that are FREE and work great too, I'll post them later.' Did you put them in another post, or is there anything else you'd like to share with us??? Thanks for the great advice, everyone, and I look forward to learning TONS on this forum...

Have a great weekend, everyone.


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## Anonymous (Feb 23, 2008)

I saw Noxx and goldsilverpro were interested in high(er) concentrations of H2O2. Just thought I would shed light on it. It can be found in 1 gallon jugs in a thick plastic bag. Non-Chlorine pool shock. Something like this http://www.archchemicals.com/Fed/BAQCIL/Products/coreProducts.htm . It claims 27%. It costs always less than 20USD. Remember, this ain't the stuff granny used to wash her mouth out with. It's the real deal. It will bleach any part of your body a brilliant white from the smallest droplet. Often unnoticed until you feel the wasp sting you! Be careful and have fun.


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## Lou (Feb 23, 2008)

Yep, and it's been mentioned quite a few times elsewhere on the site! 

There may even be a better source according to one member! Stay tuned!


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## ddrew (Mar 13, 2008)

Lou said:


> Yep, and it's been mentioned quite a few times elsewhere on the site!
> 
> There may even be a better source according to one member! Stay tuned!



I've been going through this scenario, and unfortunately I don't have a 1,000' clear zone (even though I have 10 acres of land), so that leads me to more conventional solutions. 

I'm considering building a fume hood, using 1/4" tempered glass on the front, with plywood sides and pleated furnace air filters for particulate capture, and venting back and down into a 'Negative Air Machine', like a CRSI 2000. They're selling used on eBay in the $2-300 range, with another 200 for freight. These are commonly used industrial ventilation units used in a variety of applications. It has a HEPA filtration of 99.97%. The duct work would be aluminum, since the CRSI unit is also made of aluminum. I understand there are some corrosion issues with Aluminum and some of the fumes generated, and I'm curious if going to light gauge stainless for the ductwork and input side of the CRSI unit would be worth the investment?

Does anyone have any experience with this kind unit, and whether a HEPA filtration system is sufficient to control the fumes typically created in a gold & PGM refining operation? 

That also leads to another question about disposal of the filters when they are full. Will burning the filters liberate the fumes (or underlying chemicals) and start the problems all over again?


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## goldsilverpro (Mar 13, 2008)

You will have corrosion problems with ANY metal, including stainless.


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## ddrew (Mar 13, 2008)

goldsilverpro said:


> You will have corrosion problems with ANY metal, including stainless.



What is the 'Best Practice' currently used in industry for fume hood construction? I used to do EHS work in the Air Force, and really want to do this right, if I start doing this. 

Thanks in advance for any and all suggestions.


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## Lou (Mar 13, 2008)

Epoxy paint over stainless, or enamel over stainless is what is used for typical fume hoods, both have limitations. No HF with enamel or glass, but you can use perchloric and chlorine dioxide with enamel, but not with epoxy (but you can use HF with epoxy).

The ideal material is a fluoro polymer, like teflon.

http://www.scicominc.com/teflon_film.htm

For the duct work, I recommend PVC over stainless, aluminum, and anything else--for the price and easy of construction, it can not be beaten.


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## ddrew (Mar 13, 2008)

Lou said:


> Epoxy paint over stainless, or enamel over stainless is what is used for typical fume hoods, both have limitations. No HF with enamel or glass, but you can use perchloric and chlorine dioxide with enamel, but not with epoxy (but you can use HF with epoxy).
> 
> The ideal material is a fluoro polymer, like teflon.
> 
> ...



Thanks Lou, that's a great idea. Since this doesn't rely on a specific substrate, I think I'll use Plywood to build the hood, and then cover it with this. I can find better uses for the Aluminum or Stainless. I seem to remember that wood was discussed in another thread about fume hoods.


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## ddrew (Mar 14, 2008)

While on the topic, I'm seriously looking at a 'Negative Air Machine' that will provide the filtration and airflow for my fume hood. It's a commercial unit used in Asbestos Abatement, and duct cleaning. It uses a HEPA filter and has two pre-filters. I plan on using a pleated filter for the first pre-filter, for capturing any airborne PM's, but am looking at using an Activated Carbon refillable secondary pre-filter to capture most of the fumes before getting to the more expensive HEPA cannister filter. 

Is that worth the extra effort? I've read that Activated Carbon will capture a significant amount of the noxious fumes, and since that filter is refillable, I can change the carbon out more frequently (using an approved full face mask, of course). The HEPA Cannister Filter is costing almost as much as the Negative Air Machine itself (I'm buying it used from a house cleaning co), and I want to keep it functional as long as I can. 

This Negative Air unit is a 'Dri-eaz DefendAir XL' and has 550 cfm of airflow at load, and 985 cfm free flow. It's a portable unit that will roll under my bench and seal it's air intake (on the top of the unit) under an airtight seal on the bottom of the fume hood. The working area of the fume hood will be 3' wide and 1 1/2' deep and 3' tall, with a 'slot type' opening in the back for exhaust down to the Negative Air Machine. I'll cover all the inside of the fume hood with the teflon film recommended in a prior post. 

The books I've been reading on hood design give a design criteria of 120 cfm per sq ft of work area (using an open tank design). I think that is sufficient for a small scale 'recreational' refining operation. 

My plan is to build a functional fume hood using repurposed materials and low cost used equipment (this machine was on craigslist - newer version on eBay for $385). I'll draw plans and provide them to the forum when I'm done.

I'd appreciate any and all critiques of my design and plans.


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## Blacktoadd (Sep 9, 2008)

Having a fume hood is a minimun, I agree with that 100% You will also find that some fumes always get away from you. Some fumes go up, and some go down, from your fume hood you need a duct to the ceiling, and also one to the floor. Little note: Inside the fume hood a little shelf in fromt of the fan is a good place to place the flat pie plates from corning you get from Good will. the air going across them evaporates down any solutions you want very rapidly, and free. If shelf is close to fan, and a cover top and sides are added high velocity across the top of the surface of the pie plate evaporates nearly as quick as bunsen and beaker. All of the floating crystols that form will be in a pile on the far side of the plate, doing a little separation as well. I love free processes and stuff. Sometimes dilute liquids can be evaoporated for free, heat the acids off. everythng will be in bottom. a little cheap acid will remove base metals leaveing values behind, all separaded.


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## Blacktoadd (Sep 9, 2008)

There is a nice product, PVC foam core with two shiny sides in board form. It can be bent simply by placing a 2x4 on each side of a bend line and heating the crack with a heat gun. When sofe bend and hold a few min. It can be solvent cemented or screwed together. It can he heated between two sheets of plywood or sheet rock or whatever and wrapped around anything to from cheap plastic duct of any size.


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## viacin (Oct 5, 2008)

lazersteve said:


> and when using AR you'll have Chlorine gas also.



Isn't that mustard gas?


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## Lou (Oct 5, 2008)

No, that is bis(2-chloroethyl) sulfide. Please use a search engine next time.


Chlorine, a product of many of our processes was used as a war gas, but it was largely ineffective compared to other gases.


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## viacin (Oct 5, 2008)

I did use a search engine. I'm not a scientists so 

"The sulfur mustards, of which mustard gas (bis(2-chloroethyl) sulfide) is a member, are a class of related cytotoxic, vesicant chemical warfare agents" doesn't tell me much. Your no sufficed.


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## Lou (Oct 5, 2008)

Relax, do not take offense.

I'm not trying to argue, it just seems like you said "isn't that [chlorine] mustard gas" only to say it. 

I guess my point is that you don't need to be a scientist to figure out that chlorine is not a mustard agent based off this:
"The sulfur mustards, of which mustard gas (bis(2-chloroethyl) sulfide) is a member, are a class of related cytotoxic, vesicant chemical warfare agents"


As for the big words, just search them up or use common sense and figure them out contextually. Hopefully, you'll never need to know more about that compound anyway!


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## viacin (Oct 5, 2008)

lol sorry lou. Took it the wrong way. And you're right, This is as mucha s I need to know about it  

common sense isn't always my strongest point anyway, but I make up for it with book smarts 8)


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## wop1969 (Feb 21, 2009)

If the AR fumes could be moved thru water that is impregnated with say
agricultural lime (CaO), crushed limestone (CaCO3) or sodium bicarbonate (NaHCO3) would the NITROGEN DIOXIDE fume be nutralized?

Also is their any chance that the NITROGEN DIOXIDE fume could react to the water? I have read that it does not like water ???


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## Noxx (Feb 21, 2009)

Yes part of it would be. But I'm not sure how much though.


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## Anonymous (Jun 17, 2010)

If anyone is still looking for higher concentration H2O2, go to a health food store and ask if they have "food grade" hydrogen peroxide. It should be 35%. As with any other chemical read the MSDS first--this stuff will eat your skin!


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## solar seeker (Aug 1, 2010)

I have been working outside to avoid the fumes generated and I've been doing my best to capture the fumes in glass apple cider jugs in order to recycle the fumes back into nitric acid while reducing the environmental impact as much as possible. It is unfortunate in my opinion that NOx fumes are dangerous because the sweet smell and taste of this gas makes the fumes almost pleasant to be around in extremely small quantities. This sweet smell makes NOx fumes all that much more dangerous because the senses that provide warnings about dangers in the air are registering very little to no danger when in fact you're being slowly ,or in some cases rapidly, poisoned. It's this lack of warning that makes these fumes so dangerous especially to those who haven't read or don't pay attention to the warnings 
written all over the internet.


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## rfd298 (Aug 2, 2010)

I too work outside when dealing with any chemical products. The little scents off of AR I catch smell exactly like the exhaust from my 2009 diesel standard firetrucks. Both are bad for you, and I avoid breathing them both as much as possible.


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## goldenchild (Aug 2, 2010)

solar seeker said:


> It is unfortunate in my opinion that NOx fumes are dangerous because the sweet smell and taste of this gas makes the fumes almost pleasant to be around in extremely small quantities. This sweet smell makes NOx fumes all that much more dangerous because the senses that provide warnings about dangers in the air are registering very little to no danger when in fact you're being slowly ,or in some cases rapidly, poisoned.



It IS crazy that such a poisonous gas smells nice. AR is at least very pungent and burns your nose. And clorox + HCL... forget about it!


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## Barren Realms 007 (Aug 2, 2010)

goldenchild said:


> It IS crazy that such a poisonous gas smells nice. AR is at least very pungent and burns your nose. And clorox + HCL... forget about it!



If you are working outside put a hose hold box fan blowing the fumes away from you.


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## wade brenckle (Jun 18, 2012)

I picked a old small refriderator off the side of the road. Put it on its back, put a few inches of water,my 5 gal bucket, with a few rams and pins. pured on the real AR when the red fumes started closed the box for 24 hours. no fumes, no pins just some green liquid a blank ram sticks. works for me. Is there a bad side to this the book said the water absorbes the fumes? the system was drained because i scraped the compressor for the copper (brown gold to me)


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## butcher (Jun 18, 2012)

The NO2 fume’s would need bubbled through the water for the water to absorb them which would make dilute nitric acid in solution, NO fumes would have to be mixed with oxygen to form NO2 gas before the water would absorb it, the surface of the water may dissolve some of these fumes very slowly, but I would not think the water could absorb much of them, I suppose that the refrigerator could have formed dripping condensation that these gases that could mixed with, or the gases may not have gone into solution much at all, and just changed forms from the red brown gas that normally evolves in the reaction, one way to tell is try measuring the pH or specific gravity of the water. Another possibility maybe if there were exposed metals the fumes may have just made salts of the exposed metals until fumes were consumed.


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## Richard NL (Dec 6, 2014)

WARNING: No "cartridge type" respirator will filter out nitric fumes, NONE!!!

"Activated Carbon will capture a significant amount of the noxious fumes"
And it is the missing ingredient for a out of control fire when working with NOx gases.


BFRC= http://tinyurl.com/nlrsu8t
No that wasn't mine BFRC, LOL!!!

A leak in a nitric acid plant in Geleen, there has escaped a large amount of nitrogen dioxide on April 9, 2010. The red / brown cloud is nitrogen dioxide. 

Search and learn before you die !!!
Stay safe and take care.


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## PalladiumPrincess (Dec 8, 2020)

Has anyone tried adding conc. H2O2 to aqua regia before? I am trying to better dissolve tungsten and I have seen in a few spots that the addition of H2O2 to aqua regia can help with this but I am worried about whether or not this process is dangerous? I am not too keen on adding an oxidant to a superacid. If anyone has tried this I would really appreciate concentrations used and a description of how the reaction went. Thank you!


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## Martijn (Dec 9, 2020)

Hi PalladiumPrincess, Welcome to the forum. 
First, the thread you are referring to originated from 2007. Since then some new insights, best practices and preventive control measures may have become the consensus. 

We tend to avoid creating BFRC, because a BFRC means a lot of nitric goes up in 'smoke' and is thus wasted. to achieve this: don't add large amounts of HNO3 to the solution, and never pre-mix AR, unless you know it will all be consumed and leave some metal untouched. 
next: use scrubber flasks with a dry trap in between to catch harmful fumes before they are released to the environment. (and your lungs) forget cartridge respirators. Prevention and containment is key. 

Have you read the first page of this thread? Post 11 from goldsilverpro mentions this excact H2O2 addition and how it works.
It basically supplies an abundance of oxygen to the AR, regenerating the NO in to NO2, which can be absorbed by the solution, reusing the nitric. 
How were you planning on creating said BFRC? what kind of 'ore' material? how much? which process will be used? 
Ask here on GRF before creating a big problem you can't get out of anymore. 
Have a plan before you start!! Stay healthy and alive! 

Martijn.


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## PalladiumPrincess (Dec 13, 2020)

Thank you for your reply Martjin! 
If you do not mind me asking, what does BFRC stand for? (I am new to many of the acronyms used). 
I have access to a chemical hood and I am planning to use about 15 mL of AR to dissolve about 0.5 grams of material in a beaker ( do not have scrubber flasks). I was going to try adding about 5 mL total of 30% H2O2 (dropwise) to the solution in order to better dissolve the tungsten in the material. But I want to be sure before I do this that it is safe to do so. 
I did see the post about how the reaction works but I am having trouble finding information on how dangerous H2O2+AR is? For example, is 20 mL in a fume hood considered dangerous?
Will there be a large amount of heat generation and/or fumes? 
And I am wondering how long the solution remains active and what the proper disposal of such a solution is if anyone knows this?
I appreciate any guidance at all! Thank you


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## FrugalRefiner (Dec 13, 2020)

PalladiumPrincess said:


> Thank you for your reply Martjin!
> If you do not mind me asking, what does BFRC stand for? (I am new to many of the acronyms used).



See A Glossary of Common Terms for acronyms and terms you don't know.

In this case it's the Big Freakin Red Cloud of NO2 fumes that evolve from nitric acid reactions.


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## PalladiumPrincess (Dec 13, 2020)

Thank you FrugalRefiner for the clarification. I am wondering though if adding H2O2 to AR will form BFRC? According to the post by goldsilverpro (» June 22nd, 2007, 12:50 am) on the first page of this forum the H2O2 works to reduce the fumes. I am wondering if anyone here has experience with this particular solution? I am a little apprehensive since there is very little published literature on the topic. (In particular safety). 

Thank you again and I appreciate any guidance on the topic!


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## Martijn (Dec 15, 2020)

I have no experience with adding H2O2 to reduce NO2 fumes.I try to avoid it by taking it slow with additions of HNO3. 
But adding H2O2 should be done slowly because it can cause some heat and reaction i have understood it well. 
Start small and get experience with small amounts in large beakers with room to spare. 
Martijn.


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## Shark (Dec 15, 2020)

Here is a video by metalicmario, known on the forum as goldenchild. I posted the link to the YouTube page since there is a few comments worth looking into.


https://www.youtube.com/watch?v=8PhE7GIUrxA


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## Hartbar (Jun 13, 2021)

I just read this entire thread.
I’ve dissolved some silver in 50/50, nitric acid/distilled water. Outside.
Hoping to get some karat gold going in aqua Regia.
My question is, what happens to these fumes, do they drop, or rise and go where?

Again, I’m outside.


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## FrugalRefiner (Jun 13, 2021)

Hartbar said:


> My question is, what happens to these fumes, do they drop, or rise and go where?



Watch someone smoking a cigarette. The smoke they breathe out is at first visible, because it is concentrated. But then it kind of disappears... But it's only being diluted. All of the smoke particles are still there, but as they become more diluted as they spread, they're no longer readily visible. It's the same with your fumes. They're still there until they react with something. Ideally it will be in your fume scrubber. In the worst case it will be in your lungs.  Whether they rise or drop depends on the fumes you produce, but they should all be treated.

Dave


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## Hartbar (Jun 14, 2021)

The fumes I produce so far are:
From 50% nitric acid 50% distilled water, being used to dissolve sterling silver.
I’m about to try AR, nitric and hydrochloric on karat gold and gold filled.
I understand everyone’s mention of fume hood and scrubber. At this point I don’t have facilities for one.
However, I am doing this outside, with two large fans blowing fumes away and hopefully up.


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