AIR SUPPLY
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A particular problem that surface dwellers
virtually never face
is inadequate air supply. In many underground
situations, of
course, this is not a problem either:
an underground chamber
may be so large that
even the presence of many creatures does
not consume oxygen faster than it can
be replaced; or natural or
artificially channeled ventilation may
insure that old air is steadily
replaced with new.
The potential for air supply problems beneath
the surface
should not be overlooked. If a cave-in
occurs, ventilation sources
may be cut off; if a chamber is small,
it may become so crowded
that a meager ventilation system is incapable
of replacing oxygen
as fast as it is depleted. In any event,
air supply is occasionally a
factor in underground adventuring.
1.1 Duration
Assuming no ventilation whatsoever, a
human-sized creature
at complete REST depletes the oxygen in
<a 10' cube of air: -x> within
24 hours. If the creature performs even
moderate physical activity, <define moderate>
the duration of air supply is reduced
to 12 hours. If the creature
spends its time
in any kind of strenuous exertion, the
duration of the air supply is reduced
to a mere six hours.
If a character spends some time engaged
in heavy or light
exertion and rests at other times, simply
calculate the oxygen
consumption in multiples of the resting
rate. Thus, a character
who is working strenuously uses oxygen
four times faster than a
resting character, and a moderately exercising
character uses
the oxygen up twice as fast as a character
at rest. A character
who rests for three hours and then works
hard for five hours has
used up as much oxygen as he would in
23 hours (3 hours + 4 x 5
hours) of REST.
A DM can apply this ratio to all characters
and to any creatures,
such as mules
or dogs, that accompany them. An accurate duration
figure can be achieved by figuring the
weight of the creature
into human equivalents. A dwarf or elf,
for example, consumes 213
as much oxygen as a human, while a halfling
or a dog uses only
half as much. A mule or an ogre,
on the other hand, consumes
oxygen at twice the rate of a human.
A character does not instantly die when
his air supply has been
used up, but serious problems arise. Each
turn following the
exhaustion of the oxygen, the character
must make a CON
Check. Every time the check fails, each
of his ability scores
and his hit point total are reduced by
one. Each additional CON
Check is made against the reduced CON
score.
Thus, a character grows more and more
feeble as he gulps the
last remnants of the oxygen supply. When
all of a character’s ability
scores have dropped to 0, he is unconscious.
When a character’s
hit point total reaches -10, he is dead.
Even for a character
with a large number of hit points, this
fate becomes automatic
once the CON
score reaches 0, since all further CON
Checks automatically fail. This system
is used only for characters
in an area with air; it cannot be used
for characters who are
holding their breath.
If fresh air is introduced to a character
before death occurs, he
begins to recover immediately. Hit points
and ability scores all
climb at the rate of three points per
turn until the character
reaches his original levels in all areas.
Fire
is a more voracious consumer of oxygen than even the
most heavily working
character, and consequently presents a
severe threat to
characters in situations of limited air supply.
Even a flickering
torch can. create problems in a small chamber
that has little
or no ventilation.
A small fire (one
foot or less in diameter) consumes all of the
oxygen in a ten-foot
cubic space in two hours (1 2 turns). A flaming
torch consumes all
of the oxygen in the same space in eight
hours. Of course,
when all of the oxygen is consumed, the fire
goes out. The oxygen
consumption of larger fires is based on the
number of small
fires they equal. A fire four times larger than a
small fire consumes
oxygen four times as fast.
A flask of burning
oil does not burn for very long, but uses up a
lot of oxygen while
it burns. In general, oil in a flask or similar
small container
burns for three rounds. For purposes of oxygen
consumption, however,
treat the burning oil as a small fire (as
explained above)
and treat each round of burning as a full turn.
Thus, an oil fire
that lasts three rounds uses up as much oxygen
as a small wood
fire burning for three turns.
The smoke that accompanies fires causes additional problems.
While fire
consumes the oxygen that characters need to
breathe, smoke acts
as a poisonous gas that fills enclosed areas
and is unavoidably
inhaled along with any remaining oxygen.
While it is possible
to burn extremely dry and flammable materials
with little or no
smoke, most fires are not this efficient. If any
of the fuel for
the fire is wet, or if green or living branches, twigs,
or leaves are used,
smoke is produced. Any kind of burning fabric
creates smoke, as
does burning oil.
The average amount
of smoke produced by a small fire in one
turn is enough to
create a one-foot-thick smoke layer in a 10 foot x
10 foot square AREA.
The smoke rises to the highest part of a room
and collects in
a layer against the ceiling. The next turn’s worth of
smoke collects immediately
below the first layer, and so on, until
the breathable air
is concentrated in the few feet nearest the floor.
Finally the entire
room fills with smoke and even characters lying
on the floor are
affected.
An oil fire creates
the same amount of smoke as an average
fire, except that
in an oil fire the rate is calculated by round
instead of by turn.
The smoke rate of a larger fire is calculated just
as the oxygen consumption,
so a fire that is three times as big as
a one-foot-diameter
fire creates smoke three times as fast.
A character forced
to breathe smoke must make a CON
Check each round that the smoke is inhaled.
A failed check
means that he suffers
ld6 hit points of smoke damage.
Smoke damage is
temporary. If a character has a chance to
breathe fresh air,
the smoke damage goes away at the same rate
that it was acquired-i.e.,
the character makes a CON Check
every round of breathing fresh air, with success meaning
that he has regained
1d6 points. Although temporary, smoke
damage is real in
the sense that any other damage taken while a
character suffers
from smoke damage must be considered
cumulative with
it. Example: A character who has a total of 33 hit
points loses 28
of them due to smoke inhalation. If he gets struck
by an orc for 5
points of damage before he has had a chance to
regains any of his
smoke damage losses, he is killed.
1.4 Poisonous and Noxious Gases
"... I do not like the smell of the left-hand way: there is foul air down there, or I am no guide." - Gandalf, The Fellowship of the Ring
Gases can originate from a number of underground
sources.
Volcanic
activity can create deadly emissions of sulphuric gas that are every
bit as poisonous as the bite of a venomous creature,
while garbage || sewage can generate noxious
gases such as methane whose smells are so overpowering that characters
have a difficult time breathing them.
The occurence of such gases is primarily a campaign function to be handled by a DM at the appropriate time.
Poisonous Gases: As in most situations
involving poison,
poisonous gases generally require
characters to make saves vs. Poison.
Noxious gases: Noxious
gases should force characters to make CON Checks every round;
failure results in a general lowering
of ability scores by <3> three,
with a similar penalty applied to attack
rolls.
The modern example of tear gas falls into
this category.
Characters can be rendered quite helpless
by the effects of noxious gases (when all ability scores are reduced to
0),
but they are not killed because there
is no loss of hit points.
Ability scores are raised at the rate
of <3> three per turn when the character has a chance to breathe fresh
air again.
Modifiers to the saving throw or Constitution
Check can be applied as the DM sees fit,
to account for exceptionally lethal or
mild poisons or to simulate degrees of noxiousness.
Certain types of gases,
such as natural gas,
are either odorless or possess such a
mild odor that the characters may not be aware that the gas is present
until they start making checks or saving throws.
Other types of gases,
such as sulphur,
carry such a strong
odor that the characters might have a chance to hold their breath
<link> before the full force of the gas can take effect.
Natural Gas:
Natural gas,
often encountered in regions where coal
&& oil are common,
has the additional hazard of being explosive.
If characters encounter natural gas and
are carrying a torch,
candle,
lantern or any other source of open flame,
the natural gas has a base 20% chance
per round of exploding.
Such an explosion causes 1d6 points of
damage to all characters and creatures in the AREA containing the gas.
Characters entering a region containing
natural gas in such quantities might be allowed to make Wis Checks if they
are moving slowly and investigating their surroundings carefully.
More heavily concentrated natural gas,
or other types of explosive gases,
are possible.
The DM can modify the gas's chance of
exploding and damage inflicted upward as follows:
each 10% increase in the chance of explosion
adds another d6 to the damage inflicted to the characters.
Higher concentrations should also increase
the character's Wisdom scores by 1 per 10% potency increase,
for purposes of this Wisdom Check only.
Note that if a gas is completely odor-free,
no WIS Check should be allowed,
since the check represents the character's
awareness of the gas's odor and an odorless gas gives no opportunity for
a check.
Any gas,
whether poisonous,
noxious,
or harmless,
can cause problems to characters by replacing
the oxygen in a given AREA.
In this case,
the effects should be treated as if part
or all of the oxygen in a location has been used up,
as explained earlier. <link>
Certain creatures,
most notably small birds,
are more sensitive to poisonous gases
than humans and other character races are.
If,
perchance,
a party has a small bird with them and
becomes exposed to a gradually increasing amount of poisonous gas (not
including noxious gases),
the DM should make a secret saving throw
vs. poison for the bird <1> one turn before the characters must save.
The bird saves as a 0th-level human,
and if the saving throw fails,
the bird dies.
Note that this procedure is of little help
if gas is suddenly introduced to an area in high concentration.
The party must encounter a gradually increasing
amount of gas in order for a bird to provide any early warning.
SUMMARY
* Characters can be rendered quite helpless
by the effects of noxious gases (when all ability scores are reduced to
0), but they are not killed as there is no loss of HP.
* If characters encounter natural gas and
are carrying a torch, candle, lantern or any other source of open flame,
the natural gas has a base 20% chance per round of exploding.
* Such an explosion causes 1d6 points
of damage to all characters and creatures in the AREA of the gas.
* The DM can modify the gas's chance of
exploding and damage inflicted upward as follows: each 10% increase in
th chance of explosion adds another d6 to the damage inflicted to the characters.
* Higher concentrations should also increase
the character's Wisdom scores by 1 per 10% potency increase, for purposes
of this Wisdom check only.
* The bird saves as a 0th-level human, and if the saving throw fails, the bird dies.
SUMMARY
* Smoke from small fires
or torches does not accumulate in moderately ventilated areas,
while smoke from large fires
or from burning oil only accumulates at 1/2 the rate listed for enclosed
areas.
* No matter how long or how winding the
connecting passages may be, these AREAS collect <l> smoke from small
fires at 1/2 the rate previously listed.
* <l> Poisonous or noxious gases remain
in such an AREA for 2-5 hours (1d4+1).
* <l> Poisonous or noxious gases remain in such an AREA for 2-5 hours (1d4+1).
* <l> Poisonous or noxious gases, unless specifically noted as being heavier than air, remain in such an AREA for 24 hours.
* <l> Smoke that collects in such a room lingers for 1d6 hours after the fire that created it goes out.
Ventilation of an underground area depends
on several factors.
Chief among these is fresh air flowing
into and through the
AREA. Any underground chamber with a noticeable
airflow is considered
well-ventilated. Smoke
does not accumulate in such an
area, nor is the oxygen exhausted by characters
breathing or by
fire. The duration of all gas-based spells
is halved in such an
area. Poisonous or noxious gases remain
in a ventilated area for
two turns unless more of the gas is introduced.
More subtle air movement can be detected
by the flickering of
a torch or candle. Even when characters
cannot discern this
movement through their own sense of touch,
fresh air for breathing
is not a problem in these areas. Gas-based
spells linger for
their normal durations, and poisonous
or noxious gases remain
effective for one hour.
Smoke from small fires or torches does
not accumulate in moderately
ventilated areas, while smoke from large
fires or from burning
oil only accumulates at 1/2 the rate listed
for enclosed areas.
Some areas appear to contain no ventilation,
but are actually
connected either to ventilated areas or
to the earth’s surface. No
matter how long or winding the connecting
passages may be,
these areas collect smoke from small fires
at 1/2 the rate previously
listed. Large or oil fires fill the area
with smoke at the usual
rate. Characters do not use up all of
the air through breathing;
even this minimal amount of ventilation
allows enough air movement
for respiration. Poisonous or noxious
gases remain in such
an area for 2-5 hours (1d4+1). The duration
of all gas-based
spells is normal.
An area that contains no noticeable ventilation
and has no
place for smoke to flow out horizontally
or upward captures
smoke at the normal rate (even from small
fires). Poisonous or
noxious gases, unless specifically noted
as being heavier than
air, remain in such an area for a full
24 hours.
Areas that are completely sealed off from
any outside passages,
either through cave-ins, constructed barriers
such as mortared
stone walls, or magical barriers such
as walls of force, are
subject to all of the effects listed,
at their normal rates of accumulation
and effect. The air supply is finite,
and once used up, cannot
be replaced except through the introduction
of fresh air.
Smoke that collects in such a room lingers
for 1d6 hours after
the fire that created it goes out. Poisonous
or noxious gases
remain in the area until vented out by
the admission of fresh air.
Again, the duration of all gas-based spells
is normal.
1.6 Odor
Detection
The sense of smell,
while relatively insignificant when compared
to those of sight and sound,
occasionally provides a character
with advance warning of some nearby hazard
|| obstacle.
This sense is only useful to a character
when no other overpowering
scent is in close proximity to him or
permeating the AREA.
The basic procedure
for a character to detect an odor is a WIS
Check made when the scent is first encountered.
Another check may be made if the scent
grows very strong, or a change in the wind carries it to the character
with increased force.
Of course, this WISCheck
should be made by the DM so
that the players are not alerted that
they should be on the lookout
for something. The reason that the check
is not repeated more
frequently is that if an odor is not noticed
when it is first encountered,
it will probably not be noticed thereafter
unless something
occurs to draw the characters' attention
to it.
If the party has any dogs
accompanying them, the DM may
also check for the dogs if they would
be alerted by the scent. The
scent of a monster would almost certainly
alert them, for example,
while the odor of a campfire probably
would not. Dogs are all
assumed to have a Wisdom
of 16, for purposes of this check only.
If a dog smells something, the DM should
describe the dog's
reaction in appropriate terms: a growl
of warning, perhaps, or a
cringe of fear. If a dog has been trained
to react in a certain way,
then this reaction should be used. Sophisticated
responses
require considerable training, however,
and should only be used
if the dog has been trained. <note:
i'm sure that some other AD&D monsters,
psb. incl. ferrets/weasels, are noted as having a strong sense of smell>
The WIS Check is only
made using the character's full WIS
score if the odor is strong enough to
be easily noticed. The
strength of an odor is obviously going
to req. a DM judgment
call, but general guidelines (for distance,
type of odor, etc.) and
WIS modifiers are given in Table 15: Odor
Detection.
If a dog
is making the check, double the distacne listed before implementing the
negative modifiers.
Distance from Character
| Source of Odor | 1-120 ft | 121-360 ft | 316-1000 ft | 1000-5000 ft |
| Fires: | - | - | - | - |
| small | 0 | -4 | -8 | - |
| large | +2 | 0 | -4 | -8 |
| oil | +4 | +2 | 0 | -4 |
| conflagration | +8 | +4 | +2 | 0 |
| Odorous gas | +4 | +2 | 0 | -4 |
| Creatures: | - | - | - | - |
| strong-odor | 0 | -2 | -6 | -10 |
| mild-odor | -2 | -6 | -10 | - |
| no-odor | -6 | -10 | - | - |
| Cooking food | +2 | 0 | -2 | -6 |
<update table to incl. a M fire category>
The number found by cross-referencing the
source of the odor
with the character’s distance from the
source of the odor is a
modifier to the Wisdom Check. A “-” indicates
that the odor
cannot be detected that far away.
Small
fires
are used for cooking or keeping a small group of
individuals
warm. They are generally one foot or less in diameter.
Large
fires
are bonfires, large campfires, funeral pyres, and
other
relatively sizeable but controlled blazes. A large fire can be
6-8
feet in diameter, with the flames rising even higher.
Oil
fires are fires where oil, creosote,
or coal is burning.
Some pungent chemicals,
when burned, create fires in this category.
Conflagrations
are huge fires, often burning
out of control.
A large boat, a
bridge, or a building creates a conflagration when it
burns.
Odorous gases are those with distinctive smells, such as sulphur || methane (swamp gas).
Strong-odor
creatures use an odor as a means of marking terrain
(such as males among
the great cats) or defending themselves
themselves
(such as skunks).
The area near the lair of such creatures
always carries this distinctive scent,
but it is only 50% likely to be
encountered if the creature is prowling
outside of its lair.
Mild-odor creatures
are those whose living quarters or presence
is generally accompanied by a distinctive
odor. Pigs, while
relatively clean animals, nonetheless
tend to emit a fairly strong
odor around their lairs. Most herd
animals, especially those kept
domestically by intelligent creatures,
emit some sort of lair odor.
Bands of orcs or other humanoid types
with somewhat casual
personal hygiene habits fall into this
category as well.
No-odor creatures
are those that take care to remove sources
of odor from their lairs. Humans
fall into this category, as do birds
and reptiles.
Cooking food
is just that.
If any currents of air are prevalent in
the underground area, the
wind direction can serve as an additional
modifier. Table 16:
Wind Effects on Odors
lists the modifications to the distances at
which odors are detectable. If a distance
is listed as “1/2,” for
example, the distances for each of the
categories listed on Table
15: Odor Detection should
be reduced to 11/2 of the original.
Table 16: WIND
EFFECTS ON ODORS
Direction of Source
| Wind Force | Upwind | Crosswind | Downwind |
| Strong | Normal | 1/2 | No detection |
| Medium | Double | 1/2 | 1/10 |
| Light | Double | Normal | 1/4 |
Upwind sources mean that the wind is blowing
from the direction
of the odor’s source toward the character.
Downwind means that the wind is blowing
the odor away from the character, and
crosswind means that the wind is blowing
perpendicular to the
direction between the character and the
source of odor.
Strong winds are those capable of extinguishing
torches and
other small fires, and of raising clouds
of dust.
Medium winds cause torches to flicker,
and extinguish small flames such as candles.
Light winds are almost unnoticeable to
characters.
<define winds in terms of mph>
