September 2010
NIOSH Publication Number 2010-168c

Sulfur dioxide

Synonyms & Trade Names
Sulfurous acid anhydride, Sulfurous oxide, Sulfur oxide
CAS No.
7446-09-5
RTECS No.
WS4550000
DOT ID & Guide
1079 125
Formula
SO2
Conversion
1 ppm = 2.62 mg/m3
IDLH
100 ppm
See: 7446095
Exposure Limits
NIOSH REL
: TWA 2 ppm (5 mg/m3) ST 5 ppm (13 mg/m3)
OSHA PEL
†: TWA 5 ppm (13 mg/m3)
Measurement Methods

NIOSH ID200
Physical Description
Colorless gas with a characteristic, irritating, pungent odor. [Note: A liquid below 14°F. Shipped as a liquefied compressed gas.]
MW:
64.1
BP:
14°F
FRZ:
-104°F
Sol:
10%
VP:
3.2 atm
IP:
12.30 eV
Fl.P:
NA
UEL:
NA
LEL:
NA
RGasD:
2.26
Nonflammable Gas
Incompatibilities & Reactivities
Powdered alkali metals (such as sodium & potassium), water, ammonia, zinc, aluminum, brass, copper [Note: Reacts with water to form sulfurous acid (H2SO3).]
Exposure Routes
inhalation, skin and/or eye contact
Symptoms
irritation eyes, nose, throat; rhinorrhea (discharge of thin nasal mucus); choking, cough; reflex bronchoconstriction; liquid: frostbite
Target Organs
Eyes, skin, respiratory system
Personal Protection/Sanitation
(See protection codes)
Skin: Frostbite
Eyes: Frostbite
Wash skin: No recommendation
Remove: When wet or contaminated (liquid)
Change: No recommendation
Provide: Frostbite wash
First Aid
(See procedures)
Eye: Frostbite
Skin: Frostbite
Breathing: Respiratory support
Respirator Recommendations

NIOSH

Up to 20 ppm:
(APF = 10) Any chemical cartridge respirator with cartridge(s) providing protection against the compound of concern*
(APF = 10) Any supplied-air respirator*

Up to 50 ppm:
(APF = 25) Any supplied-air respirator operated in a continuous-flow mode*
(APF = 25) Any powered, air-purifying respirator with cartridge(s) providing protection against the compound of concern*

Up to 100 ppm:
(APF = 50) Any chemical cartridge respirator with a full facepiece and cartridge(s) providing protection against the compound of concern
(APF = 50) Any air-purifying, full-facepiece respirator (gas mask) with a chin-style, front- or back-mounted canister providing protection against the compound of concern
(APF = 50) Any powered, air-purifying respirator with a tight-fitting facepiece and cartridge(s) providing protection against the compound of concern*
(APF = 50) Any supplied-air respirator that has a tight-fitting facepiece and is operated in a continuous-flow mode*
(APF = 50) Any self-contained breathing apparatus with a full facepiece
(APF = 50) Any supplied-air respirator with a full facepiece

Emergency or planned entry into unknown concentrations or IDLH conditions:
(APF = 10,000) Any self-contained breathing apparatus that has a full facepiece and is operated in a pressure-demand or other positive-pressure mode
(APF = 10,000) Any supplied-air respirator that has a full facepiece and is operated in a pressure-demand or other positive-pressure mode in combination with an auxiliary self-contained positive-pressure breathing apparatus

Escape:
(APF = 50) Any air-purifying, full-facepiece respirator (gas mask) with a chin-style, front- or back-mounted canister providing protection against the compound of concern
Any appropriate escape-type, self-contained breathing apparatus

Important additional information about respirator selection

See also: INTRODUCTION   See ICSC CARD: 0074