Once again this group has hit the nail on the head! You guys are amazing!
At this point, in the conversation with the college, we are moving to using carbon dioxide. With my and the course instructors experience, we are hoping for CO2 cylinders at each bench and tubing to each station with clamps to shut the
flow when needed. I'd like to try out the alka seltzer option! But, we don't have experience with that one yet, so that might be a supplement.
I did some field work with ether this week. This and FlyNap pose problems that I'm not confident ventilation can solve in this setting. Substitution to the lesser hazard, being carbon dioxide gas, transfers the operational costs from the
college level to the department level in this case. But, the potential exposure to hazardous emissions is like night and day.
This would make a great case study! Thanks for the advice everyone.
Ellen
That's the problem I wrote about. HVAC people usually can't do this or don't do it well. And the problems with doing it right are legion. For example, someone
suggested a slot vent at the back of each bench. In order to draw the length of the bench, they are going to need a somewhere between 1000 and 2000 fi/m slot face velocities and either partial enclosure at the back of the table or three slots to accommodate
the diffusion by evaporation of solvents on the bench. We are already into a lot of custom metal work and sight line problems for the instructor in the class.
So these slots have to draw a lot of air, and with 12 to 14 students in the room that will be gassing fruit flies, even if you branch duct 6 slot hoods together and
have a centerline velocity of 3000 f/m in the duct to cut down on diameter, you are looking at finding a chase to the roof for two ducts that are probably 20 inches in diameter or more. Add that to the fume hood ducts that also need to go to the roof and
you have a major chase design issue. Say nothing about energy cost for heating and cooling.
And in my other email, I provided the basic formula for doing it by dilution ventilation and that also requires a lot of air and energy.
A laboratory in which there is bench work CANNOT be designed until the users tell the designers exactly what they intend to do on those benches and with what chemicals.
There is no ASHRAE lab one-size-fits all as soon as bench work is done. And using solvents of any kind on open benches is going to be expensive.. Fine with me --- I get paid for working out a good hood for the proposed work and the specs for the engineers
who do the system.
But clearly, if you can kill critters other ways and don't do it, you sure aren't part of the green revolution.
> >Avoid using hazardous chemicals for such a task.
>
While this is a reasonable response, as has been demonstrated by the many posts about the disadvantages of ethyl ether and possible alternatives, I know that this particular teaching lab has been doing this work with ethyl ether for at least 40 years. The use
of ethyl ether has been discussed by many generations of lab instructors with many generations of EHS professionals (including me).
The fact that the use of ether persists suggests that it would be prudent to design the lab ventilation system to manage ether. Even if the next generation of lab instructors decide to move to a different agent, it's possible that the one after that will return
to ether. There are few EHS staff that have the authority to force specific changes on managers of lab processes.
- Ralph
Ralph Stuart, CIH, CCHO
Environmental Safety Manager
Keene State College
603 358-2859
ralph.stuart**At_Symbol_Here**keene.edu
