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Methyl mercaptan

HMT 15 June 2026

UN / ID: UN 1064
Hazard class: 2.3
Packing group: —
ERG guide: ERG 117
Special provisions: SP 3, SP B7, SP B9, SP B14, SP N89, SP T50
Source: 49 CFR §172 (15 June 2026)

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Methyl mercaptan

Methanethiol ( METH-ayn-THY-ol), also called methyl mercaptan, is an organosulfur compound with the chemical formula CH3SH. It is a colorless flammable gas with a distinctive putrid smell. In small amounts, it is pervasive in nature and found in certain foods, such as some nuts and cheese. It contributes to many odors, including the emissions from pulp mills, bad breath, and flatus Wikipedia

Substance Data

Source: PubChem (HSDB, 22.10.2026)

CAS-Number

74-93-1

Flash Point

-18 ° C

Boiling Point

5.95 ° C

Emergency Response Guide No. 117

Hazardous Materials Table

Source: 49 CFR §172 (15 June 2026)

(3) Hazard class

2.3
Poisonous gas

(4) Identification number

UN 1064

(5) Packing Group

—

(6) Labels

(7) Special Provisions (§172.102)

×Note:
Special provisions may be very complex. The extracts are taken from 49 CFR §172.102. Please be careful with the information, as necessary, additional conditions may be applied that are not written here. Please check the original source and report bugs.

3	This material is poisonous by inhalation (see § 171.8 of this subchapter) in Hazard Zone C (see § 173.116(a) of this subchapter), and must be described as an inhalation hazard under the provisions of this subchapter. Browse special provision 3
B7	Safety relief devices are not authorized on multi-unit tank car tanks. Openings for safety relief devices on multi-unit tank car tanks shall be plugged or blank flanged. Browse special provision B7
B9	Bottom outlets are not authorized. Browse special provision B9
B14	Each bulk packaging, except a tank car or a multi-unit-tank car tank, must be insulated with an insulating material so that the overall thermal conductance at 15.5 °C (60 °F) is no more than 1.5333 kilojoules per hour per square meter per degree Celsius (0.075 Btu per hour per square foot per degree Fahrenheit) temperature differential. Insulating materials must not promote corrosion to steel when wet. Browse special provision B14
N89	When steel UN pressure receptacles are used, only those bearing the “H” mark are authorized. Browse special provision N89
T50	When portable tank instruction T50 is indicated in Column (7) of the § 172.101 Hazardous Materials Table, the applicable liquefied compressed gas and chemical under pressure descriptions are authorized to be transported in portable tanks in accordance with the requirements of § 173.313 of this subchapter. Browse special provision T50

(8) Packing Authorizations (§173.***)

(8A) Exceptions	None
(8B) Non-bulk	304	see 49 CFR §173.304
(8C) Bulk	314, 315	see 49 CFR §173.314, 315

(9) Quantity Limits

(9A) Passenger aircraft/rail	Forbidden
(9B) Cargo aircraft only	Forbidden

(10) Vessel stowage

(10A) Location

Stowage category “D” means the material must be stowed “on deck only” on a cargo vessel or on a passenger vessel carrying a number of passengers limited to not more than the larger of 25 passengers or one passenger per each 3 m of overall vessel length, but the material is prohibited on a passenger vessel in which the limiting number of passengers is exceeded.

Source: 49 CFR §172.101(k)

(10B) Other

40	see 49 CFR §176.84

Source: 49 CFR §176.84

Segregation chart for load, transport, and storage

This chart shows whether loading, transport, or storage with other hazard classes is permitted, prohibited, or restricted. Based on 49 CFR §177.848.

Note: In this segregation and separation chart are HazMat of hazard class 2.3 considered depending on their poisonousness by inhalation (Hazard zone A/B). See PHMSA Interpretation #09-0252.

Scope & sources (important)Click to show CFR references

This check evaluates segregation per 49 CFR §177.848. Additional loading/unloading and handling requirements may still apply; see 49 CFR §177 Subpart B (Loading and Unloading):

§177.834 - General requirements
§177.835 - Class 1 materials
§177.837 - Class 3 materials
§177.838 - Class 4 (flammable solid) materials, Class 5 (oxidizing) materials, and Division 4.2 (pyroforic liquid) materials
§177.839 - Class 8 (corrosive) materials
§177.840 - Class 2 (gases) materials
§177.841 - Division 6.1 and Division 2.3 materials
§177.842 - Class 7 (radioactive) material
§177.843 - Contamination of vehicles

Similar substances

UN / ID	Proper shipping name	Hazard class
UN 3071	Mercaptans, liquid, toxic, flammable, n.o.s. or Mercaptan mixtures, liquid, toxic, flammable, n.o.s., flash point not less than 23 degrees C	6.1
UN 1228	Mercaptans, liquid, flammable, toxic, n.o.s. or Mercaptan mixtures, liquid, flammable, toxic, n.o.s.	3
UN 3336	Mercaptans, liquid, flammable, n.o.s. or Mercaptan mixture, liquid, flammable, n.o.s	3
UN 1670	Perchloromethyl mercaptan	6.1
UN 1111	Amyl mercaptan	3
UN 2347	Butyl mercaptan	3
UN 3054	Cyclohexyl mercaptan	3
UN 2363	Ethyl mercaptan	3
UN 2337	Phenyl mercaptan	6.1