Safety Tidbit 3.38 – Spill Concentration
Just a little math and chemistry this week. I had a client ask about the concentration of a chemical after they spilled it and what they should do. Also, I attended a respirator course this week and the instructor just happened to put up a slide talking about the exact same thing. I guess, I was meant to use the topic as my Safety Tidbit for this week.
First, the scenario: a full 100-milliliter flask of toluene is dropped (and broken) in a space 10-feet x 10-feet x 8-feet high. We will assume no ventilation and complete mixing throughout the space and normal temperature and pressure. The molecular weight of toluene is 92.1 and its specific gravity is 0.87. So, what is the highest possible ambient concentration (in parts per million PPM) of toluene in the space?
Calculations:
Room Volume = 10x10x8=800 ft3 or 22,656 liters
Weight of Toluene spilled = 100x0.87=87 grams
Moles of Toluene = 87/92.1 = 0.94 moles
Total evaporated volume in liters = 0.94x24.2 = 22.75 liters
Percentage of spill in air = 22.75/22,656 = 0.001
Parts per million = 0.001 x 1,000,000 = 1000 PPM
If we look at OSHA requirements the 8-hour time-weighted average Permissible Exposure Limit is 200 PPM, the acceptable ceiling concentration is 300 PPM, and the Maximum Peak that shall not be exceeded for 10 minutes in any 8-hour shift is 500 PPM. Coincidentally, 500 PPM is also the NIOSH IDLH or the level that is immediately dangerous to life or health.
To advise my client as to how to handle their circumstance, I told them to turn on their exhaust ventilation to pull out the toluene. However, if they needed to go into the space right away they would need either supplied air or an SCBA to enter. Bottomline, it doesn’t take much chemical to significantly contaminate the environment.
Hope this was helpful and thank you for reading my Safety Tidbits! Comments and questions are always welcome. ~ Bryan
P.S. If you have an interesting safety or health question please let me know.
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