Hazardous Atmospheres

Earth’s atmosphere is 78% nitrogen and 21% oxygen (plus 1% com-
prising a number of other gases). Visitors to other planets (and victims
of lab accidents or death traps) might encounter other atmospheres,
most of which are unsafe for humans without proper protection. Of
course, “breathable air” for humans might be deadly for nonhumans,
and vice versa!
Corrosive: The atmosphere reacts with exposed flesh. Those with the
Sealed advantage are safe; those in sealed suits might be safe, but some
gases eat away at seals. Small concentrations in otherwise breathable
air require a roll at HT to HT-4 every minute to avoid 1 point of corro-
sion damage. Victims suffer coughing (see Afflictions, p. 428) after los-
ing 1/3 their HP, blindness (as the disadvantage) after losing 2/3 their
HP. Atmospheres made up mostly of corrosive gases have effects com-
parable to immersion in acid (see Acid, p. 428) and count as suffocat-
ing. Corrosives include ammonia and nitrides. Chlorine and fluorine
are extremely corrosive and toxic!
Toxic: The atmosphere is poisonous. Individuals without respirators,
Doesn’t Breathe, Filter Lungs, etc. are susceptible. Ordinary airborne
industrial pollutants might require a daily HT roll to avoid 1 point of
toxic damage. Lethal gases would call for a HT-2 to HT-6 roll every
minute to avoid 1 point of toxic damage. If such gases make up most of
the atmosphere, they inflict at least 1d toxic damage per 15 seconds (no
resistance possible) and count as suffocating. A typical toxic gas is car-
bon monoxide. Chlorine and fluorine are deadly in tiny concentrations,
and also corrosive.
Suffocating: The atmosphere is unbreathable. For humans, this
means it lacks oxygen. Those without Doesn’t Breathe or an air supply
start to suffocate (see Suffocation, p. 436). Hydrogen, methane, and
nitrogen are all suffocating. As noted above, an atmosphere made up
mostly of corrosive or toxic gases is suffocating as well – but these usu-
ally kill so rapidly that suffocation becomes irrelevant.