IRSST - Institut de recherche Robert-Sauvé en santé et en sécurité du travail

 Important Notice Concerning COVID-19

Due to the rapid spread of COVID-19, and to ensure the health and safety of its employees and its entire network, the IRSST has implemented exceptional measures.
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On March 26, 2020, according to Decree 159-2020 published on March 11, 2020 in the Gazette officielle du Québec, the Regulation respecting occupational health and safety (RSST, RLRQ, c. S-2.1, r. 13) is amended in Appendix 1. These regulatory changes have not yet been incorporated into the current Substance Data Sheets of the Sampling Guide for Air Contaminants in the Workplace. An update is currently underway and will be available as soon as possible. Consequently, the information contained in the data sheets of substances modified or added in Decree 159-2020 is probably inaccurate or incomplete. Please contact our client service: [email protected] for further information.

Asbestos, Amosite

French name in the regulation: Amiante, Amosite
CAS : 12172-73-5
Synonyms: Mysorite

Exposure Standards in RROHS regulation

Permissible exposure values (PEV)
ppm mg/m3 f/cc Notes
TWAEV - - 0,2 2a , 2b , 3
STEV - - 1 -
Ceiling - - - -
Simple asphyxiant Percutaneous
Minimum exposure  Sensitizer
Prohibited use Prohibited recirculation
Carcinogenicity C1

TWA adjustment for unusual work schedules

III : Weekly adjustment

CNESST – Toxicological Index Service

Consult REPTOX file: Asbestos, Amosite


Numération de fibres

Method: IRSST - 243-1
Sampling device:
Sampling media required:
918 Cassette with conductive extension and MCE, 25 mm, 0.8 µm

Flow rate: 0,5-16 L/min
TWA sampling volume: 400 L
STEL sampling volume: -
Remarks: Open cassette sampling. A flow rate not exceeding 2.5 L/min is recommended for determining an average concentration. Supply at least 2 blanks per series of samples or 10% of sample total, whichever is highest. Send the samples in a cardboard box supplied by the IRSST (#3010). In relatively uncontaminated atmospheres, where the fibre concentration is much lower than 0.1 fibres/mL, use larger sampling volumes (3000 to 10000L) in order to obtain quantifiable densities.
Principle: Phase contrast optical microscopy (PCM)
Remarks: The method applies to the counting of all fibres whose refractive index is compatible with the mounting solution. The minimum reported value is 9 fibres/mm². Characterization of the fibres in bulk samples or in deposited dusts is done using method 244. An analysis using a transmission electron microscopy (TEM) method may be required for some materials containing fine asbestos fibres, for example floor tiles.
IRSST. "Numération des fibres". Méthode 243-1. Méthodes analytiques. Montréal: IRSST, 1990.