When to replace respirator filters?

Question

I've got a respirator like this one:

I assume with the particulate filters (for dust) you just change them when they get hard to breathe through, but what about the organic vapor or chemical cartridges? How do you know when they need to be replaced?

Answer 1

You are correct regarding the dust filters... in fact the "caking" particles can sometimes improve filtration... so the cartridges only need to be replaced when damaged, soiled or when they unacceptably obstruct breathing.

As for chemical filters... this depends a great deal on the chemicals being dealt with, as each will have different properties.

Each cartridge should have a specified service life or change schedule... nonetheless, for vapors and certain organic compounds 3M™ recommends that they be used for only a single shift exposure

Can chemical cartridges be used for more than one shift?

Organic vapors are removed by the process of adsorption. Weak physical forces hold the organic vapor on the activated carbon. Since these forces are weak, the process can be reversed and the organic vapor can be desorbed. Desorption during storage or nonuse periods can result in the migration of the chemical through the cartridge. Migration is mainly a concern only for organic vapor cartridges. Organic vapors adsorbed on an organic vapor cartridge can migrate through the carbon bed without airflow. Desorption of very volatile contaminants can occur after a short period (hours) without use (e.g., overnight). Partial use of the chemical cartridge and subsequent reuse could potentially expose the user to the contaminant. This is most significant for the most volatile and poorly retained organic vapors (e.g., boiling point < 65°C). For organic vapors with a boiling point less than 65°C, it is recommended that the organic vapor cartridge never be used longer than one shift even if the estimated service life is greater than 8 hours and the cartridge is used for only a short time during the shift.