Hi,

I posted some questions here last year about recirculating direct fired heaters:

http://hvac-talk.com/vbb/showthread.php?t=480782

Since then I have learned quite a bit about these units and the standards that govern them, for instance that there isn't a corresponding CSA standard to ANSI Z83.18, like there is with non-recirculating direct fired heaters ANSI Z83.4 CSA/3.7

I'm curious how most of the engineers and professionals feel about using direct fired units, when the amount of pollution that is allowed is substantially higher than what ANSI/ASHRAE 62.1 recommends (CO/NO2), or outbreaks of respiratory illness have been attributed to amounts of nitrogen dioxide less than the room concentration that ANSI Z83.18 allows of 3 ppm?

Health professionals I talk with are solidly on 1 page it seems, and engineers are on another in regards to air contaminant concentrations.

I've seen the argument posted, that no one has gotten ill from direct fired units. I would say that most people who work under one of these death units doesn't even know that their being polluted with CO/NOx and ultra fine particulates, so their doctor would have no idea to connect conditions from multiple sclerosis, to hearing impairments and a myriad of other diseases that can be chronically induced by the pollution at the levels that these units are allowed to emit.

I'm open for comments on the following article:

http://brownair.net/blog/2011/03/31/...xide-monitors/

Thanks!