what is the TWA in alberta?

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# Part 3 Specifications and Certifications (cont.) ## Specifications and certifications (cont.) Section 16 OCCUPATIONAL HEALTH AND SAFETY CODE Part 4 AR 191/2021 # Requirements Applicable to All Industries # Part 4 Chemical Hazards, Biological Hazards and Harmful Substances ## General Requirements ## Worker exposure to harmful substances - 16(1) An employer must ensure that a worker's exposure to any substance listed in Schedule 1, Table 2 is kept as low as reasonably achievable. - 16(2) An employer must ensure that a worker's exposure to any substance listed in Schedule 1, Table 2 does not exceed its occupational exposure limits listed in Schedule 1, Table 2. - 16(2.1) The amended occupational exposure limit for coal dust as shown in Schedule 1, Table 2 comes into effect on July 1, 2010. - 16(3) If no occupational exposure limit is established for a harmful substance present at a work site, an employer must ensure that a worker's exposure to that substance is kept as low as reasonably achievable. - 16(3.1) A worker may not be exposed to a substance listed in Schedule 1, Table 2 at a concentration exceeding its ceiling limit at any time. - 16(4) If no 15-minute occupational exposure limit or ceiling occupational exposure limit is listed for a substance in Schedule 1, Table 2, the employer must (a) comply with the 8-hour occupational exposure limit, and (b) ensure that a worker's exposure to that substance does not exceed (i) 3 times the 8-hour occupational exposure limit for more than a total of 30 minutes during a continuous 24-hour period, and 5 times the 8-hour occupational exposure limit, or (ii) the concentration that is immediately dangerous to life and health, whichever is lower. ## Exposure to multiple substances - 17 An employer must take all reasonably practicable steps to ensure that, if a worker is exposed to more than one substance listed in Schedule 1, Table 2 during a single work shift, and the toxicological effects have simi…