Canada Road & Rail Transport - Class 2 Lethal Concentrations

As mentioned earlier in the course, the abbreviation LC₅₀ refers to a measure of a lethal concentration for gases, vapours, dust, or mists, certain types of which can be lethal when not diluted by air. To ensure that these lethal concentrations are not present during transport, the TDG Regulations require determination of the LC₅₀ values for both single and pure gases and mixed gases. These values may be found in one of the following sources:

• In CGA P-20, ISO Standard 10298, technical journals, or government publications
• In accordance with paragraphs 2.2.3(b) and (c) of Chapter 2.2 of the UN Recommendations

For a mixture of gases, the LC₅₀ values may be approximated by using the methods shown in Part 2, Section 2.17, of the TDG Regulations. To use these methods, the LC₅₀ values of each gas in the mixture must be known.

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