Local exhaust ventilation effectiveness.. to odour limits..

[jamesbanda]

dear all,

we need to install lev on a new system to drum off a waste material. the industrial hygene limit is 50ppm-100ppm but the odour limit is 0.01 to 0.06ppm (depending on which msds you read..)..

so we are working with the chemical supplier on the system design - how pratical is it to design to 0.01 ppm limits.. the chemical at atm pressure 20c has a vapour pressure such that the atm concentration is 10000-20000 ppm..(from an aspen sim with air purges)..
dropping 7 orders or purity with an lev seems very diffuclt..

is this stuff going to smell when we exchast it.. it is a very pungent odour.. so i'm wondering if we need odour abaitment.. eg a carbon bed..?

james

 

[quark]

As far as health effects are concerned, TEL is good enough. Low odour threshold doesn't mean that we have to operate the system odour free.

In a IH perspective, TEL to OT ratio of more than 1 is always good and reduces human exposure to great extent (becuase of unpleasant smell). You have more problems when the ratio is less than 1.

I would prefer either to automate the system to minimise human interaction or using suitable PPEs if human interaction is necessary.

Reducing concentration to odour threshold levels seems to be redundant and quite difficult.

 

[Latexman]

IMO, TEL is not good enough (no one likes to work in a toilet/sewer all day) and the odor free boundary depends on how frequently this operation is done.

Very frequently - automate and use engineering controls. We deal with a few really smelly monomers in my business and we have a vent incinerator on site. I've visited other's plants that did not take this seriously, and I wanted to burn my clothes before going home. I know for a fact they had odor issues brewing with their neighbors. I would not work permanently in those places if they did not plan on going odor free.

Occaisionally - make it more manual with the proper PPE so the operator doesn't smell it. Proper PPE includes uniforms and boots the company takes care of. Use engineering controls so the odor is not detected outside of the immediate area of operation.

Good luck,
Latexman

 

[jamesbanda]

letexman,

I'm advised by the iH guys that work with LEV systems that the system we plan to use for our smelly chemical is adquate.. but the technicals are very doubt full that it will fully remove the odors..

whats your take on the effectiveness of lev systems..

 

[Latexman]

They are effective as long as the design is sound and they get used properly. Many years back, an IH guy gave me a copy of "Industrial Ventalation" by the ACGIH. It's an excellent reference with lots of Go-Bys and examples. I've had good success with designs using methodologies from this guide. The biggest issue in my experience is folks not using PPE and engineering controls properly. They take shortcuts.

Good luck,
Latexman

 

[chicopee]

I have been told by sewage treatment plant operators that after a while they do not mind the smell eventhough they work in sewage all day long. So smell appears to be only a state of mind.