1.  The specific gravity of methane is _________.

2.  The specific gravity of carbon dioxide is _________.

3.  The specific gravity of carbon monoxide is _________.

4.  _________ is a mixture of carbon dioxide, nitrogen and air which is oxygen deficient.

5.  Smoke usually contains _________ _________ and other toxic or asphyxiating gases produced by fires.

6.  Breathing air containing _________ _________ carbon dioxide causes violent panting and can lead to death.

7.  The first symptom of _________ _________ poisoning is a slight tightening across the forehead and possibly a headache.

8.  High temperatures (or heat) cause gases to expand so they _________ more quickly.

9.  It is much _________ to remove a concentration of a light gas like methane by ventilation than it is to remove the same concentration of a heavier gas like carbon dioxide.

10.  Small hydrogen _________, known as hydrogen "pops" are fairly common in firefighting.