As with cleanroom contamination, the source of failure in airlocks or anterooms is human behavior. Bioburden is the number of bacteria living on a non-sterilized surface and is the primary source of cleanroom contamination.
There are many methods and processes involved in controlling microbes in a cleanroom, including the use of an anteroom, airlock, or vestibule. Whether your facility comprises a stringent airlock or simply designed isolation space of an anteroom, the transitional space’s effectiveness in protecting the critical areas of your cleanroom most often fail due to humans failure to follow procedure. Herein, we refer to the transitional space as an anteroom though it may be an airlock or vestibule.
An anteroom is a space between a completely uncontrolled environment and a monitored controlled environment. The transitional space exists to protect the controlled environment from contamination. Often, it is clear to cleanroom staff about their roles in the cleanroom, but less clear how their actions when inside the anteroom preparing to enter the controlled areas can impact the safety of the facility’s products.
The role of an anteroom as an isolation space is accomplished by having 2 doors that make the space a closed area. Its 2 doors should be interlocked to prevent them from both being open simultaneously. More stringent anterooms may have a controlled supply of air for ventilation with filtered air being pumped in and exhaust air exiting in a controlled manner. Proper design of ventilation for any anteroom is vital as it improves the area’s ability to prevent airborne contaminants such as chemical fumes, particles, or microbial organisms from filtering into the critical environment.
But even with excellent, effective anteroom design and well-written cleanroom gowning procedures, the system can fail due to human error. We discuss some of the most common preventable behaviors that cause contamination of a cleanroom or its products.
Activities of people and equipment occurring within the anteroom and the cleanroom should impact the designed airflow of these areas as little as possible. A design flaw often encountered is permitting a horizontal surface to be placed in front of the exhaust air openings. This encourages workers to deposit materials, supplies, and other items onto the trolley, table, or shelf placed in that area that may obstruct the exhaust partially or completely causing a change in airflow that results in contaminants lingering rather than being removed from the area.
Avoid placing equipment and fixtures in areas that impede the designed airflow and if you discover these tempting horizontal surfaces are in the airflow zone, resist using it to deposit anything that will further reduce airflow or add contaminants. Avoid placing trash receptacles near vents.
The first line of defense against humans contaminating critical areas is cleanroom apparel. But mishandling of cleanroom clothing during gowning in the anteroom can be a significant source of contamination with particles and microbes.
Properly following cleanroom donning and doffing procedures is challenging and presents the most opportunity for improvement in almost every facility. Comprehensive and periodic training with practice can help to identify issues that may impact your facility’s products and ultimately, consumer safety.
Cleanroom coveralls present significant challenges because they are large and often the material is difficult to gather completely and securely into your hands. If any part of the coverall touches the floor, a new coverall is required.
Another issue with coveralls is that, once donned, if the wearer moves too quickly particularly in a downward movement, the body moving against the inside of the coverall can cause the air to compress and be released at the collar into the anteroom or cleanroom. This release of contaminants is sometimes referred can be more easily controlled by using the correct size of coverall, wearing cleanroom undergarments instead of personal undergarments, and the wearer using purposeful controlled movements.
In fact, using controlled movements at all times in the anteroom and cleanroom is one of the ways to avoid many situations that result in human contamination of the environment. Whether a cleanroom worker is involved in a production shift, cleaning, or simply moving to and from the area, slow minimal movement is key.
Not only do controlled movements minimize expelling contaminants from within cleanroom garments but also prevent re-introducing contaminants from the floor that have been deposited there by the design of the cleanroom or anteroom airflow. Clean air enters from the ceiling area and exhausts as close to the floor as possible so contaminants are forced to the floor. Walking too fast can cause the contaminants to become airborne increasing the chances of unsafe product contamination.
Coughing and sneezing are difficult-to-control movements that can be violent as human movements go. Specific guidelines about this human behavior are up to the facility’s SOP, but it is important that the procedures do give consideration to these inevitable behaviors and offer solutions.
One option that is practical and second-nature to most is to use cleanroom wipes like one would use a tissue. When the urge comes to sneeze or cough, the worker can reach for a wipe to hold in front of their mouth and nose to collect the droplets.
A best practice is to return to the anteroom to remove the wipes from the face and dispose of them properly outside the critical area. Note after such an event, any contaminated cleanroom apparel such as face masks, gloves, or hoods must be changed with proper apparel removal and donning procedures before returning to the critical area.
A better alternative, if it is possible such as having just entered the critical area is to return to the anteroom to cough or sneeze so that the cleanroom has less chance of contamination. Keep in mind that coughs and sneezes can deposit contaminants up to 25 feet or more away as well as cause particles and microbes to be airborne.
Another difficult-to-control movement is scratching. Not only are itches sometimes persistent, but scratching them can be a behavior you are unaware of especially for those new to working in a controlled environment. But, scratching inside the critical area is just not acceptable or safe. If it is required, it is vital to return to the anteroom to scratch. Keep in mind that this may require replacement of cleanroom apparel.
Akin to scratching, the urge to adjust safety goggles or reposition another piece of protective equipment may be both insistent and a movement you are unaware of. Any adjustments to clothing or PPE should be done inside the anteroom.
Inside the anteroom or your critical areas, never lean over the product, process, or cleaned/sanitized surface.
Doing so results in the designed laminar airflow that is designed to force contaminants downward to the floor to blow over the cleanroom staff before the intended surface. This introduces significant potential of contamination not only because of the particles and microbes shed from the staff but also because the airflow becomes interrupted and can actually stir up contaminants.
Image credit: By Rudolf Simon, M+W Group GmbH, Stuttgart, Germany – Own work, CC BY-SA 3.0
Since cleanroom staff must move in the facility, contamination is always a possibility even when the movements are slow and controlled. Hygiene guidelines help minimize human contamination.
When most people think about hygiene, they think about removing contaminants from the body through washing and cleansing. And this is important for cleanroom staff. But it is not just removing dirt, oils, hair, skin cells, and germs from the body, and especially the hands, but also being aware of what you do not put on the body.
Using specialty cleanroom cleansers and sanitizers that do not introduce chemicals, fragrances, and other potential contaminants is helpful. Cleanroom workers should not use cosmetics, body care products or hair care products such as lotions, sprays, mousses, or powders.
Jewelry is an attractant for particles and microbes so it should not be worn into the anteroom or cleanroom. Also, nail polishes, artificial nails, and even long nails are sources of contamination that should not be in a cleanroom. It is a newer trend so worth a mention that eyelash extensions are to be avoided.
Each time a cleanroom worker can remove something that harbors possible contaminants, she or he is taking a step toward a safer environment.
In addition to keeping movements controlled, it is vital to not have too much commotion or oppositional air movement going on in the anteroom or cleanroom. One way to control this is to limit the number of staff that are permitted to be present at one time.
Ensure this information is in your SOP and your personnel know this limit and follow it.
Our cleanroom-trained consultants can help you with any questions you have about cleanroom contamination and help you determine the best products for your needs. Ask for free samples before you buy.