NIOSH Pocket Guide to Chemical Hazards


CAS 50-00-0


RTECS LP8925000
Synonyms & Trade Names
Methanal, Methyl aldehyde, Methylene oxide
DOT ID & Guide


NIOSH REL: Ca TWA 0.016 ppm C 0.1 ppm [15-minute] See Appendix A
OSHA PEL: [1910.1048] TWA 0.75 ppm ST 2 ppm
IDLH Ca [20 ppm] See: 50000 Conversion 1 ppm = 1.23 mg/m3
Physical Description
Nearly colorless gas with a pungent, suffocating odor. [Note: Often used in an aqueous solution (see specific listing for Formalin).]
MW: 30.0
BP: -6°F
FRZ: -134°F
Sol: Miscible
VP: >1 atm
IP: 10.88 eV
RGasD: 1.04

Fl.P: NA (Gas)
UEL: 73%
LEL: 7.0%

Flammable Gas
Incompatibilities & Reactivities
Strong oxidizers, alkalis & acids; phenols; urea [Note: Pure formaldehyde has a tendency to polymerize. Reacts with HCl to form bis-Chloromethyl ether.]
Measurement Methods
NIOSH 2016, 2541, 3500, 3800; OSHA ID205, 52
See: NMAM or OSHA Methods
Personal Protection & Sanitation (See protection)
Skin: No recommendation
Eyes: Prevent eye contact
Wash skin: No recommendation
Remove: No recommendation
Change: No recommendation

First Aid (See procedures)
Eye: Irrigate immediately

Breathing: Respiratory support

Important additional information about respirator selection
Respirator Recommendations (See Appendix E) NIOSH
At concentrations above the NIOSH REL, or where there is no REL, at any detectable concentration:
(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 canister providing protection against the compound of concern/Any appropriate escape-type, self-contained breathing apparatus
Exposure Routes inhalation, skin and/or eye contact
Symptoms Irritation eyes, nose, throat, respiratory system; lacrimation (discharge of tears); cough; wheezing; [potential occupational carcinogen]
Target Organs Eyes, respiratory system

Cancer Site [nasal cancer]
See also: INTRODUCTION   See ICSC CARD: 0275   See MEDICAL TESTS: 0110