This may give a little more information.
Stability chambers bring in the opportunity of algae and other organic growth because most of ICH storage conditions do have a humidity component to the specification. Whether the humidification process is steam, ultrasonic, or saturator with dew point control – there will be wet surfaces somewhere in the conditioner or air plenums. Even some of the temperature only conditions like 5C and -20 will require a cold coil temperature with will also create water in the system.
Some of these humidification methods may require high purity water sources. While this “feed” water will generally not contain algae or contaminants, once the moisture is introduced into the air flow, it will generally cross over a cooler surface (DX coil or plenum) where temperature is lower than the dew point of the air. This will cause water to condense on the cooler surface. The air being circulated through system will pick up some contaminates either from inside the chamber or through the outside environment (fresh air make-up or chamber door openings) and growth will be more likely at the wetted surfaces.
Conditions (temperature/RH) of the chamber, temperature of the wetted surface, purity of make-up water, and the contents or activities of the chamber or surrounding area will determine growth potential of algae and other contaminants.
Best practices to reduce or even prevent growth include:
1. PMs that effectively clean and disinfect areas that are wet in the conditioner or chamber.
2. Preventing stagnate water from forming. Be sure the system has working condensate drains and that water is not forming in areas without drains.
3. If the chamber has a lot of corrugated boxes or paper, a return filter will help minimize the cellulose from the paper products which help feed growth in the wetted areas.
4. Reduce the possibility of introducing growth with the feed water by utilizing RO, chlorinated tap water (with filtered mineral content). DI water will also work but be careful that the purity level is not great to cause rapid deterioration in components.