Summary

Worker exposure to solvents, or more broadly to organic vapours, must be controlled or even kept below regulatory limits. When administrative, engineering and collective protection measures are insufficient to achieve safe exposure levels, workers must be equipped with respiratory protective devices (RPDs). In the absence of situations immediately dangerous to life and health (IDLH), RPDs with activated charcoal-based filter cartridges are used to protect against organic vapours. The question that then arises is: what is the service life of these cartridges? Among the options available for responding, implementing predictive models of breakdown times is the most used.

The objective of this project was to update Saturisk, an online tool provided by the Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST) to calculate the service life of organic vapour cartridges. The update was primarily intended to incorporate a broader range of cartridges and solvents into Saturisk. Concurrently, an experimental system based on cartridge miniaturization was developed to verify, in controlled conditions, the service lives predicted by the model.

The Wood model was selected to calculate service lives. Charcoal properties (microporous volume, structure factor) were determinable using three experimental approaches: solvent adsorption on actual cartridges, solvent adsorption on minicartridges and, the most classic, argon adsorption. Comparison of the experimental results and the results calculated by the model shows that, overall, the service lives or 10 % breakdown times are quasi-systematically underestimated by the model (approximately 0%-20 %). This represents an additional safety factor in the use of this tool to determine the cartridge replacement sequence in a respiratory protection program.

The model yields the most accurate microporous volume and structure factor values in the case of solvent adsorption on actual cartridges. More experiments would statistically verify this finding, because the microporous volume and structure factors obtained by the other two methods also yield acceptable service life estimates.

The adsorption rate, a variable of the Wood model, was determined based on two empirical calculation methods. Although the Wu method seems to improve the model’s accuracy overall, its routine use is hindered by a lack of bibliographic data on the dielectric constant of organic vapours. Consequently, the Wood-Stampfer method was selected.

Cartridge miniaturization for breakdown tests was promising. Both for determining charcoal microporous volumes and structure factors and for verifying the data calculated by the model, the findings are encouraging: the 10 % breakdown times measured experimentally for actual cartridges and minicartridges are strongly correlated. However, improvements must be made to the actual-real transposition hypotheses to achieve a better matching between these two cartridge types in breakdown curve profiles.

After it is updated, the Saturisk tool will be able to calculate service lives using a database of 167 organic vapours, taken from Schedule 1 of the Regulation respecting occupational health and safety, and 11 cartridges from seven manufacturers authorized to sell their products in Quebec. Regulatory reminders specific to certain organic vapours and conditions for RPD use, as well as limitations related to the use of models, will be provided for purposes of exercising the best judgment on the service lives calculated by Saturisk.