thats an extremely open question relevant to what situation and what is it suppressing as differing chemical have differing L.E.L`s and U.E.L`s

Have you thought of water mist? Not a gas but very effective as it reduces the oxygen content.

why another gas? why not purging with water or stem? may be helpful to remove hazard form confined space.should be quantify through RA. Regard Saif

Calvin, what is an explosion suppressant and how does it work!?! I'm intrigued. If you use it on confined space then surely you are introducing a new problem due to there being no oxygen in there for people to work? Is it that it's heavier than air and will sit there preventing oxygen from becoming part of an explosion? I do know of specialised chemicals (FM200 etc) that are used in electrical rooms to "absorb" energy in the event of fire. more detail please.

Greetings, Calvin. I agree with what's been said so far about haloalkanes. By explosion suppressant, I guess you are talking about talking about preventing a runaway reaction. In which case, keeping the concentrations above or below the flammable limits is the way to do it (preferably below for obvious reasons!). You could also think about refrigeration to reduce the evaporation rate and therefore the concentration in the space above (I'm assuming) the liquid. Another way might be to have a travelling top to reduce volume of the space above the surface. In addition to the gases mentioned, if purity of the protected substance is not an issue, diesel exhaust can be a cheap, albeit dirty, inerting gas.