Rd40 particle filter

This is a DIY particle filter with standard 40 mm thread, suitable for many half and full-face masks.

WARNING:
- only use when no certified commercial product is available due to e.g. supply shortages during a crisis and when you are very desparate!
- absolutely do not use when there are cracks, layer-separation or any other defects present in the print!
- drop each part from 2m / 6ft height onto a hard surface: if it breaks or cracks don't use it!
- use the filter until breathing gets more difficult, do not use it longer than 1 day!
- if you are using it as protection from things like saw-dust you can very carefully extract the filter material without releasing any dust, throw it away, wash and dry the filter and refill with new filter material BUT if you are using it as protection from biohazards and very toxic substances treat the whole filter as hazardous and dispose of accordingly!
- I absolutely cannot and will not garantee that this filter works at all nor can I guarant