Carbon filters are a tricky thing. You have to be on top of them otherwise, all the sudden they stop working.
I have been using carbon filters in my salt water tanks since 1991. I have a schedule when to clean them, and because I have beneficial bacteria that live in my filter substrate, and in the carbon filter itself, I have to be very careful how much I wash at any given time, if I kill off too many bacteria, then my nitrites will rise because these particular bacteria convert nitrites into nitrates. As well the charcoal filter soaks up nitrites. Once it is saturated, it will no longer hold nitrites.
Charcoal will soak up all kinds of things, it's a wonderful material. However, no matter what your literature states, no matter what the salesman tells you, a carbon filter is not going to filter NOx. And even if the carbon, because it's so porous, retains some deposited Nitric/NOx, it is not converting it to anything else.
If you read EPA requirements for industry that creates NOx gases, they require the gases produced to be vented through a fume scrubber, either a catalytic or wet scrubber. If you tried to use a ductless fume scrubber with a carbon filter, you would be fined and for good reason. It just wouldn't work.
NOx is not one of those gases that can be filtered with media. The best thing to do if you are small scale and cannot afford a fume scrubber or build one is to vent at high CFM your NOx gas directly into the atmosphere so long as it's not putting your neighbors or animal/plant life in danger. On a home scale you are producing so little NOx that it isn't going to do any harm to the environment you can measure. Not unless you are doing large quantities. I am using a fume scrubber because I produce a lot of NOx. Otherwise I would probably be directly venting as well. If you do decide to vent outside your lab, just make sure you vent using as much airflow as you can afford. The more air mixed with the NOx gas as it develops, the better. Also the velocity of the exhaust can push it higher into the air, so as it falls it is more or less harmless. Remember NOx is heavy and wants to be close to the ground.
Anyway, just my two cents.
Scott