3M 7500 series outflow filter adapter

thingiverse

This design requires flexible material for the 'insert' and 'gasket'. A user has successfully used a rubber gasket (such as a garden hose gasket) or an actual 3M mask washer for the gasket. Printing the 'insert' at 97% with rigid material also works, but may require minor adjustments to fit the adapter part. This adapter provides an attachment point to add a filter to the exhaust valve of a 3M 7500 series half mask. Normally, exhaled air is exhausted directly to the surroundings through a one-way valve. This is acceptable when using the mask for personal protection, but it does not protect the surroundings from the user. The adapter fits into the exhaust slot in the mask and offers a 3M bayonet attachment point for a filter. You can use any standard 3M port design, but something smaller is recommended. My mini filter works well, or you can try other designs like this one: https://www.thingiverse.com/thing:4219678. If your filter material has a preferred flow direction, consider it when designing the filter, as airflow through this adapter is opposite to normal use scenarios.