Atmosphere

Planets often have astmospheres. Atmosphere content and density determine whether the air is breathable by people and animals.

Density is expressed as a percentage value from 0 to 100%. Atmosphere density between 15 and 85 percent can be breathed; below 15% animals cannot draw enough air into their lungs; above 85% animals cannot force the air out of their lungs.

Atmospheric content is classified into categories.

Standard	Atmosphere is a good mix of breathable gases with few impurities.
Tainted	Atmosphere is a tolerable mix of gases to breath. Air may contain visible levels of impurities.
Exotic	Atmosphere is poisonous to people and animals but may host plant life. Environment suit required.
Corrosive	Atmosphere is poisonous to all plant and animal life. Corrosive to all equipment.
Insidious	Atmosphere is extremely poisonous to all plant and animal life. Extremely corrosive to all equipment.