Carbon filters have finite capacity based on the amount of carbon contained in the filter. Most carbon filters have recommended replacement on an annual interval. This ensures no risk of filter breakthrough or exposure. Many ductless manufacturers utilize electronic sensors to monitor the exhaust air and indicate when a filter is nearing saturation and should be changed out. Filter life is directly related to a variety of factors including; the type of chemical, the volume of chemical evaporated, frequency of use, and at what temperature is the chemical being handled during use.