DCHAS-L Archives Sep 22 2011 - Green Fume Hoods

I feel much more positive about the use of the latest Green Hood technology available from Air Master Systems Corp (Don Nelson, 231.798.1111 .ext 40). We have not felt comfortable installing the standard charcoal filter ductless hoods but we have just installed 13 Green Hoods in a less toxic situation than what you describe. The savings are quite significant in installation and operation. These guys make great conventional vented hoods as well as non-vented fume hoods so they do not push just one technology becau se that is all they have.

I take a balanced approach when evaluating wh at fume hood system to use. There are obvious exceptions to what I can simply state here: First, almost all exhaust air in most situations should be exhausted by fume hoods. So standard room exhaust required for the necessary air exchang es in a typical laboratory should be exhausted through fume hoods. Doing this let s you utilize the expensive makeup air for two purposes, air exchanges and fume h ood exhaust. After that, you need to make an assessment of the safety and costs of using various types of hoods. One factor to take into account - if you crea te a mixed environment of hoods, how well can you train your researchers to use the appropriate hood for any given procedure and how responsible are they. In o ther words, will they use the right hood?

Looking at the compounds you mentioned, on a 6' Green Hood you would capture about a kilogram of carbon disulfide or sulfur dioxide before the first set of filters were breached a nd the chemical sensors went off. There is still another kilogram of capacity in the filters after the fan and chemical sensors but I would treat the hood a s no longer usable. Knowing how much it can capture before a filter change is necessary, you can then evaluate the suitability for your own application. They have tested the capture capacity for thousands of compounds. Erlab really k new what they were doing when they developed these filters. If you call Air Mas ter Systems, they can do an evaluation of your needs and let you know which technologies will work well, conventional or their Green Hoods. They sell b oth and I have never seen them push for a Green Hood where it did not make sense.

I was also impressed with the sensitivity of the sensors. Bes ides the fume hood sensors, they also have a sensor in the hood to test the air in the lab. The lab sensor went off when they were cleaning some lab benches w ith a solvent during installation. There was not that much of an odor from the sm all amount of solvent but the sensors picked it up.

These Green Hoods ar e not suitable for all applications but they definitely have their place. There a re even some very unique nuisance situations where a conventional carbon filte r ductless hood is an appropriate solution but I am much more comfortable wit h these Green Hoods.

Ken Simolo
Chemistry
University of Rochester
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Dear colleagues:

We are in the process of building a new Laboratory and contemplating between u sing Dustless Fume Hoods vs. Ducted Exhaust Hoods. We will be using a variety of hazardous chemicals including carbon disulfide, acetonitrile, toluene, benz ene, some carcinogenic suspect chemicals, hydrogen sulfide and sulfur dioxide gases.

I appreciate sharing your experiences with ductless fume hoods and whether yo u recommend these type of hoods for hazardous chemical work using the aforementioned chemical examples as well as advantages and disadvantages of these hoods vs. the ducted exhaust hoods (safety concerns, costs, maintenan ce, etc.)

Thanks,

Michael Hojjatie, Ph.D.

R&D director, TKI

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