I've been trying to troubleshoot a vexing smell for some time now in my basement. Here's the rundown

1) smell comes from a small room containing a sewage ejector pump
2) the smell is kind of ammonia-like, a bit acrid
3) causes burning eyes, nauseau, headache
4) house has been tested for natural gas leaks - none
5) i borrowed a gas testing unit for a local university. there is no hydrogen sulfide or CO. it does not smell like rotten eggs.
6) there is a very low level of volatile organic compounds (less than 0.4 ppm)
7) i've poured water onto the top of the ejector pump seal and fixed all leaks i could find with silicone
8) i thought maybe it was a paint smell from some commerical paint i used - so i ripped out all the drywall
9) i've inspected the area for mold - no signs
10) there is a vent pipe up through the roof. it vents below the roof line and is about 10 feet from two attic fans.
11) i've poured a bleach solution down the drain to try to get rid of potential bacterial growth in the tank
12) smell is not coming from dry p traps

At this point I am thinking of getting a smoke test done to try to identify any small leaks in the venting system. I've also read that it may be a good idea to install charcoal filters on the roof vents, as the odors may be getting forced back down, especially by the attic fans. Do these seem like good ideas? Any other suggestions?

Thanks!