Ughh I need help with this riddle !!! paaa - lease !!?

[Funky[[:]

its man made, you only use it once, and when you use it you dont know you're using it, what am I ?

 

[The Question Asker :D]

c-o-f-f-i-n!..hope i helped =)

 

[grrrrr]

Man made oxygin in a submarine, you breathe it in once and your done with it.

 

[Kendyl]

coffin my friends tell this to me all the time

 

[itsalways9intheafternoon]

yeah a coffin sounds like it fits