Evapolar evaLIGHT Plus replacement evaporation cartridge. The cartridge contains a patented mineral fiber that is extremely absorbent and prevents the formation of bacteria and mold. The cartridge should be replaced approximately once a year. Depending on usage, this timeframe may vary. If the device is used for only about 4 to 8 weeks a year, a longer period can be expected. Since the cartridge also serves to purify the air, another factor is how polluted the air is, for example, in the presence of smokers.