CO2 Incubators > Control and Prevention of Contamination  »   What are sources of contamination?

1.    The most common source of contamination problems in humidified incubators is the humidity pan. The tendency is to forget about the water pan except when it is time to replenish the water due to evaporation.  Removing and cleaning the water pan is a simple task that can save time and money by preventing mold and bacteria from proliferating in this ideal environment.  Mold, bacteria and yeast will grow readily in stagnant water and simultaneously change the surface tension thereby affecting the humidity.  The addition of fungicide, for the prevention of contamination by these organisms, will also affect the surface tension of the water.  Therefore, the best way to eliminate contamination and humidity problems, is to change the water in the pan weekly after thoroughly washing it with soap and water and disinfecting it with 70% alcohol.

2.    Rubber gaskets that surround the opening of the incubator often have a green tinge to them because of the presence of mold.  Most of these gaskets are folded back on themselves forming a nice dark moist area where mold and bacteria prosper.  When doing a general cleaning of the incubator each month, it is important to clean out the tracks of the gaskets.

3.    Seams are other suspect areas.  Wherever two walls come together in the incubator, a seam is formed.  It is vital that these areas be cleaned thoroughly every month.  The easiest way to accomplish this most successfully is to use a squeeze bottle and force liquid into the crack thereby forcing any organisms out of the seam.

4.    Electrical cord ports are also problem areas.  Any opening that goes from inside the incubator to the outside has the potential area for transporting contaminants.  Each time the incubator door is opened, a vacuum is created there by drawing in outside air.  Consequently, it is important that the environment around the incubator be kept as clean as the environment within.

5.    Fans are a necessity in most incubators but they are also a breeding ground for bacteria and mold.  When cleaning the incubator, it is important to remove the fan cover and actually clean the paddles on the fan as well as the shaft itself.  If the fan gets dirty, it will not only circulate the air but also spread contaminating organisms around the chamber.  Hidden inconspicuous areas should always be considered potential problems.      

6.    Shelves and shelf runners must be cleaned and disinfected as a routine part of cleaning the incubator.  All the shelves should be removed and washed monthly and the runners cleaned as well.  Incubators which have shelf runners on false walls, present a potentially more serious contamination problem.  These false walls should be removed and the interior walls of the chamber cleaned thoroughly.  If the incubator shelves are aluminum and the rest of the incubator is stainless steel,  it is important to be aware of the following:
First, aluminum shelves give off aluminum oxide, in a humidified atmosphere, that will form a white precipitate on different areas of the incubator.  It is important to remove this precipitate by regular cleaning, because, although mold and bacteria cannot grow on aluminum oxide, the fumes can be toxic to cells in a culture.
Secondly, whenever metal touches metal there is always the chance that rust will form.  Rust to bacteria and mold is like a newly plowed field to seeds.  Always check to be sure there is no rust forming anywhere in the incubator and if it is, remove it immediately.

7.    Two Chamber incubators that are over-under can be troublesome for the following reasons.   The bottom chambers are often contaminated when the upper chamber is not because of the close proximity of the incubator to the floor.  Each time the door of the lower chamber is opened, a vacuum draws room air into the incubator.  If the floor is dirty the chance for the transfer of the contaminants is increased.  One way to resolve this problem is to put the incubator on a caster platform to raise it up off the floor and at the same time make it mobile so that the floor underneath the incubator can be cleaned regularly.  These two minor adjustments will save time, money and eliminate frustration over the long term.  

8.    Drip trays are another major source of contamination in the humidified incubator.  They are designed to collect the condensation that forms on the door and return it to the humidity pan via a plastic tube.  Remember, any area that is moist, warm and dark is a potential source of contamination.  Drip trays must be cleaned and disinfected routinely, along with the drain tubes.  The best habit to acquire is to clean the drip tray when cleaning the water pan.  Some incubators do not have drip trays because the doors are heated thereby eliminating the formation of condensation due to cold spots.