Yep it'll do that if your not in a well vented area, it displaces oxygen being heavier than air. Also if it hits an open flame it creates a gas called phosgene which was used as a chemical agent in WW1. It's nasty takes you breath away, eyes burn, nose snots up, it's a real good time. All the stores I deal with use "freon" type refrigerants (freon is duponts brand name) r22, r404a, r407a. This big cold storage wear house we used to service got a remodel and up graded to ammonia, I'm glad we had to drop them that schit will kill you faster than lightning.