Last week a customer sent us a question asking how long the 3M 2097 Particulate Mold Filters last. The answer is - it depends. Since it's a fairly common question, and "it depends" is such an unsatisfactory answer, we thought we'd explain it here in a bit more detail. The useful life of filters and cartridges is not fixed. In the case of the 3M 2097 P100 (HEPA) filters, we have two elements to consider: the filter and the charcoal layer. The P100 HEPA (which stands for High-Efficiency Particulate Arresting) filters trap dust and particles like a strainer. Once the filters have successfully blocked a large amount of particulate matter, they still won't let that material into your lungs. They do however start allowing less air to past through, and breathing will become more and more difficult. You may not notice it at first, but as the filters clog up, it will become harder to suck in a breath. Trust us, you'll notice eventually. That's when you know it's time to replace the filters. As we mentioned, the 3M 2097 pancake filters also have a thin layer of charcoal pressed inside. The charcoal is there to absorb smells and odors. It works like a sponge. And like a sponge, there is a limit to how much it can hold. Once the filters have soaked up all the organic vapors they can, you will start to taste or smell the offending item through your mask. Once you start to smell the things you are trying to block out, it is time to change your filter. Only you can tell if it is becoming difficult to draw a breath, or if smelly vapors are making their way through your mask. Now that you are aware of the capabilities and limitations of these filters, you'll recognize the signs that it is time for replacement. A little more about the 3M 2097 filters: They are different than the standard 2091 filters in that they have a layer of charcoal bonded in the middle. The 2091 filters come standard on the Lead and Asbestos Respirator Combo so they can keep out the really nasty dust such as lead and asbestos. However the 2097 filters also serves to eliminate lower levels of organic vapors that you may smell from solvents or household bleach. The 2097 filters come standard in our mold remediation kit designed specifically for removing mold from houses and other structures. This kit features the full face mask to protect the mucous membrane of the eyes from mold spores. Looking for a reliable respirator? Check out the 8233 n100 mask. This respirator is designed for those who want the highest rated by NIOSH filter efficiency in a mask. It is approved for lead abatement, metal fumes produced from welding, certain radioactive particulate material, and non-oil containing mists. Thanks for reading.