Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

How to Calculate Concentration of Vapor, Gas, Fume, Mist or Dust for LFL

Status
Not open for further replies.

IanVG

Mechanical
Jan 21, 2022
73
0
0
US
Hey everyone,

I'm stuck on a laboratory renovation determining which code from IMC 510 (Hazardous Exhaust Systems) is applicable. Per the exception listed for labs:

"Exception: Laboratories, as defined in Section 510.1, except where the concentration listed in Item 1 are exceeded or (emphasis mine) a vapor, gas, fume, mist or dust with a health-hazard rating of 1, 2, 3, or 4 is present in concentration exceeding 1 percent of the median lethal concentration of the substance for acute inhalation toxicity."

Where Item 1 is:

"1. A flammable vapor, gas, fume, mist or dust is present in concentrations exceeding 25 percent of the lower flammability limit of the substance for the expected room temperature."

I know how to find the lower flammability limit (LFL) and I know what my expected room temperatures will be. However, I do not know how to calculate the relevant concentration of the flammable materials. I'm guessing that this calculation is within the domain of mechanical design, and that I am responsible for calculating it.

The only resources I found online to this matter are this post and maybe this post. The second link is a NFPA article regarding how to calculate the maximum allowable quantity (MAQ) of chemicals in a space (also has some good commentary on the difference between chemicals in use and chemicals in storage).

Any thoughts, advice or relevant experience is much appreciated!
 
Replies continue below

Recommended for you

The LFL is based on percent by volume. So if you have a gas in air the lower flammability limit is the minimum ammount that will produce a flame if ignited. So 25% of LFL is 25% of this minimum ammount. Knowing a given mass of the gas you can calculate the volume percentage using the ideal gas equation. What is the gas and how does it get into the room?
 
Status
Not open for further replies.
Back
Top