4220 Flow Meter
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
H2S 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. H2S
Ampoule.
2. 5% by weight
lead acetate
solution.
Methane CH4Simple 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 N2Simple 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
N2O
NO2
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.
NO2 detector
tube.
Oxygen O2Colorless, odor-
less, tasteless.
Supports co m-
bustion.
1.11 Normal air con-
tains 20.8% of
O2. 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 O3Irritant and poi-
sonous. Strong
electrical odor.
Strong oxidiz er.
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