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Appendix D General Safety Procedures
D-8
Gas Chemical
Formula
Common
Properties
Specific
Gravity or
Vapor
Density
Air = 1
Physiological
Effect*
Max
Safe
60 Min.
Exposure
ppm
Max.
Safe
8 Hour
Exposure
ppm
Explosive Range
(% by vol.
in air.)
Limits
lower/upper
Likely
Location
of
Highest
Concentration
Most
Common
Sources
Simplest and
Cheapest
Safe Method
of Testing
Hydro-
gen Sul-
fide
H
2
S Irritant and poi-
sonous volatile
compound. Rot-
ten egg odor in
small concentra-
tions. Exposure
for 2 to 15 min. at
0.01% impairs
sense of smell.
Odor not evident
at high concen-
trations. Color-
less. Flammable.
1.19 Impairs sense
of smell, rap-
idly as concen-
tration
increases.
Death in few
minutes at
0.2%. Exposure
to 0.07 to 0.1%
rapidly causes
acute poison-
ing. Paralyzes
respiratory
center.
200
to
300
20 4.3
45.0
Near bottom,
but may be
above bottom if
air is heated and
highly humid.
Coal gas,
petro-
leum,
sewer gas.
Fumes
from blast-
ing under
some con-
ditions.
Sludge gas.
1. H
2
S
Ampoule.
2. 5% by weight
lead acetate
solution.
Methane CH
4
Simple asphyx-
iant.
Colorless, odor-
less, tasteless,
flammable.
0.55 Acts mechani-
cally to deprive
tissues of oxy-
gen. Does not
support life.
Probably no limit,
provided oxygen
percent-age is suf-
ficient for life.
— 5.0 15.0 At top, increas-
ing to certain
depth.
Natural
gas, sludge
gas, manu-
factured
gas, sewer
gas. Strata
of sedi-
mentary
origin. In
swamps or
marshes.
1. Combustible
gas indicator
2. Oxygen defi-
ciency indica-
tor.
Nitrogen N
2
Simple asphyx-
iant. Colorless,
tasteless.
Non-flammable.
Principal constit-
uent of air. (about
79%).
0.97 Physiologically
inert.
— — — — Near top, but
may be found
near bottom.
Sewer gas.
sludge gas.
Also issues
from some
rock strata.
Oxygen
deficiency
indicator.
Nitrogen
Oxides
NO
N
2
O
NO
2
Colorless
Colorless,
sweet odor.
Reddish-brown.
Irritating odor.
Deadly poison
1.04
1.53
1.58
60 to 150 ppm
cause irritation
and coughing.
Asphyxiant.
100 ppm dan-
gerous.
200 ppm fatal.
50 10 — — Near bottom. Industrial
wastes.
Common
air pollut-
ant.
NO
2
detector
tube.
Oxygen O
2
Colorless, odor-
less, tasteless.
Supports com-
bustion.
1.11 Normal air con-
tains 20.8% of
O
2
. Man can tol-
erate down to
12%. Minimum
safe 8 hour
exposure, 14 to
16%. Below 10%,
dangerous to
life. Below 5 to
7% probably
fatal.
— — — — Variable at dif-
ferent levels.
Oxygen
depletion
from poor
ventila-
tion and
absorp-
tion, or
chemical
consump-
tion of
oxygen.
Oxygen defi-
ciency indica-
tor.
Ozone O
3
Irritant and poi-
sonous. Strong
electrical odor.
Strong oxidizer.
Colorless. At 1
ppm, strong sul-
fur-like odor.
1.66 Max. naturally
occurring level
is 0.04 ppm.
0.05 ppm
causes irrita-
tion of eyes and
nose. 1 to 10
ppm causes
headache, nau-
sea; can cause
coma. Symp-
toms similar to
radiation dam-
age.
0.08 0.04 — — Near bottom. Where
ozone is
used for
disinfec-
tion.
Detectable
odor
at 0.015 ppm.
Table D-1 Hazardous Gases (Continued)
Gas
Chemical
Formula
Common
Properties
Specific
Gravity
or Vapor
Density
Air =1
Physiological
Effect
Max
Safe 60
Min. Exposure
ppm
Max. Safe
8 Hour
Exposure
ppm
Explosive
Range (% by
vol. in air)
Limits
lower/upper
Likely
Location
of
Highest
Concentration
Most
Common
Sources
Simplest and
Cheapest
Safe Method
of Testing