People often ask how long a respirator cartridge lasts. The answer is significantly less if they are not properly cared for. I'll admit in the past I have not been kind to my respirator cartridges. I haven't treated them well. I've finished my work and shoved them in the shed with the other painting supplies, or worse left them on the work bench in an the area I just finished painting. As a result, they haven't lasted very long. It's a waste of money, it adds plastic trash to the landfill, and it's just plain irresponsible. I'm sorry. Now that I'm a bit more knowledgeable about how they work, I find my respirator cartridges are lasting significantly longer. There is no on/off switch on these babies. They are filled with activated charcoal that traps organic vapors produced by things like paint and solvents even if you are not actively pulling air through your respirator. Left exposed to vapors - even in fairly small concentrations - the filtering properties you have paid for will be spent on the ambient air. The solution is simple - stick them in a bag. By limiting or blocking the cartridges' exposure to solvent vapors while the respirator is not in use, they will retain their ability to absorb vapors when you need them. Placing the entire respirator or pulling the cartridges and putting them into a ziplock or sealable plastic bag removes them from the contaminated air. If the filters are not exposed to an atmosphere laden with organic vapors, they will retain their efficiency and be ready for the next project. You will know it's time to replace your respirator cartridge when you can smell whatever vapor you are trying to block while wearing your properly-fit mask. The activated charcoal can absorb only a finite amount. Once the charcoal is full, vapors can pass them by and enter your lungs. In the meantime, seal them up and you'll get longer life from them. If you have other questions about respirators, filters, or cartridges, please don't hesitate to give us a ring at 1-800-829-9580.