Occupational Hazard Assessment of Hexachloroethane Smoke Devices used in military training exercises within the Canadian Armed Forces

Smoke grenades and smoke bombs are widely used in military operations to obscure visions, create concealment, and provide tactical advantages. These devices primarily contain hexachloroethane (HC), zinc oxide (ZnO) and granular aluminum. When ignited, a chemical reaction generates zinc chloride (ZnCl2) aerosol, forming a dense smoke screen. While effective for operational use, aerosol particles of ZnCl2 are considered an irritant and acute toxicity inhalation exposure can cause respiratory tract irritation and pulmonary toxicity. Recognizing these hazards, the American Conference of Government Industrial Hygienists (ACGIH) has set a short-term exposure limit (STEL) of 2 mg/m3 over 15 minutes [1] and an 8-hour time-weighted average (TWA) of 1 mg/m3. Despite existing protective measures, there is limited data on realistic exposure levels experienced during military training, creating uncertainty on respiratory protection guidance.

This study aims to evaluate the respiratory hazards associated with HC smoke grenades and smoke bombs used in Canadian Armed Forces (CAF) training and whether tactics, techniques and protocols (TTPs) can be modified to minimize the hazard. Controlled releases of HC smoke grenades and smoke pots were conducted in three scenarios: inside a controlled closed chamber, a semi open container, and a free field environment. Aerosol released from the smoke were collected at various heights by attaching air samplers to a telescopic stand, simulating different postures used in military training: prone (1’6” from the ground), kneeling (3’6” from the ground), and standing (5’6” from the ground). Additionally, an air sampler was attached to a Range Safety Officer (RSO) maintaining a proposed safe distance of 5 m away from the plume, measuring realistic exposures to HC smoke. By assessing exposure levels, the findings will help refine protective measures and establish guidelines for safe practices involving HC smoke devices used in training exercises within the CAF.

References

[1] ACGIH. Documentation of the Threshold Limit Values and Biological Exposure Indices- Zinc Chloride Fume. 2024.