NIOSH Pocket Guide to Chemical Hazards

Methyl acetylene

CAS 74-99-7


RTECS UK4250000
Synonyms & Trade Names
Allylene, Propine, Propyne, 1-Propyne
DOT ID & Guide


NIOSH REL: TWA 1000 ppm (1650 mg/m3)
OSHA PEL: TWA 1000 ppm (1650 mg/m3)
IDLH 1700 ppm [10%LEL] See: 74997 Conversion 1 ppm = 1.64 mg/m3
Physical Description
Colorless gas with a sweet odor. [Note: A fuel that is shipped as a liquefied compressed gas.]
MW: 40.1
BP: -10°F
FRZ: -153°F
Sol: Insoluble
VP: 5.2 atm
IP: 10.36 eV
RGasD: 1.41

Fl.P: NA (Gas)
UEL: ?
LEL: 1.7%

Flammable Gas
Incompatibilities & Reactivities
Strong oxidizers (such as chlorine), copper alloys [Note: Can decompose explosively at 4.5 to 5.6 atmospheres of pressure.]
Measurement Methods
NIOSH S84 (II-5)
See: NMAM or OSHA Methods
Personal Protection & Sanitation (See protection)
Skin: Frostbite
Eyes: Frostbite
Wash skin: No recommendation
Remove: When wet (flammable)
Change: No recommendation
Provide: Frostbite wash
First Aid (See procedures)
Eye: Frostbite
Skin: Frostbite
Breathing: Respiratory support

Important additional information about respirator selection
Respirator Recommendations NIOSH/OSHA
Up to 1700 ppm:
(APF = 10) Any supplied-air respirator
(APF = 50) Any self-contained breathing apparatus 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
(APF = 50) Any air-purifying, full-facepiece respirator (gas mask) with a chin-style, front- or back-mounted organic vapor canister/Any appropriate escape-type, self-contained breathing apparatus
Exposure Routes inhalation, skin and/or eye contact (liquid)
Symptoms Irritation respiratory system; tremor, hyperexcitability, anesthesia; liquid: frostbite
Target Organs respiratory system, central nervous system
See also: INTRODUCTION   See ICSC CARD: 0560