Decontamination

The decontamination of rooms is becoming a bigger issue for a diverse group of organizations such as pharmaceutical and medical device manufacturers, industrial research facilities, patient care facilities, and animal research facilities. There are more issues affecting us everyday as well as more complicated, lengthy, and expensive research that can not afford to be compromised.

The decontamination of rooms is becoming a bigger issue for a diverse group of organizations such as pharmaceutical and medical device manufacturers, industrial research facilities, patient care facilities, and animal research facilities. There are more issues affecting us everyday as well as more complicated, lengthy, and expensive research that can not afford to be compromised. Any contamination of pharmaceutical or medical devices can be potentially hazardous to patients as well as costly for producers. Compromise of the decontamination method is no longer a viable alternative.

An opportunity arose to decontaminate a 2700 cubic foot animal room with the animal racks left inside to save processing time. The current method of decontaminating the room was to remove all animals, cages, racks, etc. from the room until it was completely empty and then fog the room with an acidic chlorine dioxide solution. Once the fogging process was completed, people would enter the room and wipe down the walls to remove the residual acidic solution. To reduce the decontamination time and labor, and its associated costs, an alternative method to decontaminate the rooms was sought. As a bonus, if a method could be found that allowed the racks to be left in the room it would further save processing time.

There are various methods used by industry for decontaminating cleanrooms. These methods range from manual wiping methods, fogging methods, vapor methods, and gas decontamination. Each was evaluated to determine the best solution.

Manual wiping methods can take many forms. They either involve spraying a liquid disinfectant on all surfaces or wetting a mop or wipe and physically wiping surfaces to both physically remove organisms and apply a solution to kill organisms. The spraying method has a better chance to reach more surfaces and get a more complete coverage. Shortcomings of this are that it is difficult to spray all surfaces of complex equipment and reliance on the person applying the decontaminant to use care and not miss areas. In addition, uniform coverage is extremely difficult to achieve, and, in the areas of less coverage, the decontamination may not be as effective. From a safety perspective, unless respirators are utilized, personnel are exposed to potentially harmful vapors.

Fogging methods have some benefits compared to manual wiping methods but also some drawbacks. Automatic fogging removes the human factor where some areas might accidentally be missed but it also adds issues with complete coverage over, under, and behind components. Foggers typically take a liquid and then spray a fine mist, or very small droplets (5-100 microns) around the room. Since its sprays a liquid that is heavier than air, it tends to settle down and therefore not provide contact with all surfaces. From a safety perspective, it takes the person out of the room.

Vapor methods have some benefits compared to fogging and manual wiping methods but also some drawbacks. First we must describe that a vapor is generated from a liquid. It differs from the fogging (generating fine particle sizes) by heating the liquid till it reaches the vapor phase. This vapor is then injected into the room. The problem with vapors is that once this vapor is injected into the room it wants to return to its normal state which is a liquid. Basically any cold surfaces will condense the vapor, in effect scavenging the vapor from warmer areas. This causes uneven distribution of the vapor and concern for the overall effectiveness of the vapor. One method to help the vapor methods achieve better success is to have tight control of temperature gradients throughout the room, but this becomes difficult because a temperature gradient of as little as one degree can affect the condensation. The vapor method is typically easier and better than manual wiping or fogging. Vapor methods remove the human factor where some surfaces might accidentally be missed. From a safety perspective, it takes the person out of the room.