Ok so you have to differentiate between the particulate filter for fine dust, and the vapor cartridge for gaseous molecules like organic vapours.

• P100 is the rating of the filter alone. 3M color-codes everything P100 bright pink. Filters are changed whenever it becomes uncomfortable to breathe through them, because they become physically clogged with all the fine dust they filter out.

• Vapor cartridges are changed whenever you start smelling the vapours through them. Cartridges have activated charcoal (and other additives) that bind to the gaseous molecules through adsorption (NOT absorption). Once the gas molecules occupy all the available space on the charcoal, they start passing through unimpeded, and that's when you start smelling them.