Toxic gases

I was sleeping at my boyfriends house last night while he was on his computer and I had this dream, but I think I was half awake because I remember sensing he was at his computer.
I could smell something burning and that's what half woke me up and then I felt/smelt like toxic gas was filling the room and I tried to get up to tell my boyfriend to get out but I couldn't move or talk at all. It felt like the gas was actually drugging me unconscious.
Finally, I managed to say his name and he came over and I said to him 'fire' but he assured me there was nothing burning and I fell back asleep.
Now that I'm fully awake, it still seems so real and it was terrifying not being able to move and thinking we were slowly dying. What kind of dream was that? Would it mean anything?

What you experienced is probably "Sleep Paralysis." It's when you wake up, but your muscles are still paralyzed (as they are every night when we sleep), so you can't move. You're still dreaming, and stuck between the awake and sleep stages, I guess you could say.

Many people report having hallucinations such as demons or ghosts holding them down, heavy vibrations, or voices. The best thing you can do is be calm and wait to wake up. I fight sleep paralysis whenever I have it by trying to wiggle my toe, and slowly regaining muscle control from my foot up.

It's completely normal.

I get this all the time when I nap with other people in the room. Sometimes it is sleep paralysis, and sometimes it is just a series of false awakenings. It is such a bizarre feeling every time.