Lame Joke alert

A wet, blustery day in mid-Michigan.  Today you get a lame joke in lieu of actual content.

An explorer, lost in a blinding snowstorm in Mongolia stumbled into a nomadic camp.  They welcomed him and he eagerly went into the yurt that was warmed with an open fire in the center.

In the space of a few minutes he found himself gasping for breath and had to leave the shelter.  Concerned, his host followed him outside.

The explorer exclaimed that the gasses in the yurt were toxic.  His host disagreed, "In yurt gasses are not toxic."   He explained, "Oxygen is not in yurt."