Liquid, the ingredients are in such small ammounts that it will not hurt you at all.I researched it also and everything I read tells me there is nothing to be alarmed about at all.

The crap we breathe on the road going to work every day is hundreds of times worse for us than a thermacell every now and then.

What little odor there is is very slight. Humans put off far more alarming odors just by breathing. The thermacell odor is squat compared to our odors. Even when using scent suits.