In order to have a fire you must complete the fire triangle. You must have an ignition source + fuel + O2. If we eliminate any one of the three, there cannot be a fire.
You were given a homework assignment to draw a set of tanks which we will monitor for combustibles and O2. How do we acheive this? You only needed to make a crude drawing. Here is my crude drawing and the actual drawing and some actual pics.
Anytime you see Hg you will be dealing with vacuum. We are using an eductor to pull. I call it an aspirator.
-14.7 PSI = -30"Hg
-30"Hg = -760mmHg
What does LEL stand for?