Once contamination has hit a tissue culture incubator, it is hard to rid that incubator of the contamination.
The best way to take care of this problem is to use a 180°C sterilization cycle overnight with each hint of contamination. To see what the sterilization cycle could do to for your incubator, click here: http://binder-world.cnpg.com/Video/flatFiles/237/.
Midsci carries two incubator brands that offer this sterilization feature: The Binder 180C Sterilization incubator http://thelabshark.com/cat/prodprice2_Detail.cfm?ID=2926 and the New! Shel Lab High Heat Decontamination CO2 Incubator http://thelabshark.com/cat/prodprice2_Detail.cfm?ID=3108.
If you have an incubator that doesn't have this feature, there are a few things you can do to keep it clean and free from contamination as well:
1) The humidity pan should be removed, washed with disinfectant (non-corrosive ones!) and refilled with distilled, autoclaved water. You can also add a few pennies to the water. Copper oxide is released as the copper in the pennies breaks down. This copper oxide eliminates the microbes that are present in the chamber.
2) Remove all shelves and other stainless steel parts, wash with disinfectant, autoclave and replace into incubator as needed.
3) Wipe down the entire chamber, including door and gaskets with disinfectant as needed.
4) Replace gaskets as they wear.
5) Replace all HEPA and CO2 inline filters every 6 months or sooner, if noticeably dirty.
Depending on the amount of usage of the incubator, these processes should be done weekly, monthly or quarterly.