Identifying Contamination in the Cleanroom

November 2021 - Vol.18 No. 11 - Page #6
Category: Cleanroom Cleaning Services

Pharmacy Purchasing & Products recently held a webinar entitled:
Identifying Sources of Contamination in the Cleanroom
presented by Jim Wagner

The following questions were submitted by attendees.
The webinar slides and full presentation can be downloaded at

Q: What role does poor aseptic technique play in introducing contamination to engineering controls?

A: The most important lesson you can teach your staff is how to utilize first air properly within the primary engineering controls (PECs). All too often, staff block first air by improperly loading their components or placing items in front of the grille. The best solution for this example of poor aseptic technique is not to simply film your best technician demonstrating good aseptic technique and share that example with the staff. Rather, have your certifier conduct smoke pattern tests with every employee. It is possible to have a very full hood and operate with good aseptic technique. However, your staff must first understand the importance of product placement within the PEC. Demonstrating this via smoke pattern testing is a very effective teaching tool.

Q: What recommendations do you have for cleaning behind the hoods?

A: Ideally, every PEC should be placed far enough from the cleanrooms walls to permit thorough cleaning. Fortunately, many cleaning vendors provide cleaning tools to help access tight spaces. With laminar airflow workbenches (LAFWs), access is less of a difficulty as casters can be used to access all sides of the LAFW for cleaning.

With biological safety cabinets (BSCs), cleaning may prove more challenging. If you have a six-foot BSC in a small buffer room, access to the back of the BSC is more difficult. If you cannot find tools to solve this problem, consider sealing the BSC into place by putting fascia around the hood.

Q: If the hood is moved to clean behind it, does it then need to be recertified?

A: While recertification is not automatically required when moving the hood, two scenarios would trigger the need for recertification when moving a hood for cleaning. First, if the hood is jarred during the moving process, there could be potential damage to the seal of the HEPA filter to the unit, which could create a leak. However, if the hood is on casters, and it is only moved a few feet in order to clean behind it and then moved back, damage to the HEPA filter is unlikely. This does underscore the importance of casters; I would not recommend moving a hood that is not on casters.

The other scenario that would prompt recertification is if the hood is moved for cleaning but then returned to a different location. It is important to note that in addition to confirming proper aseptic technique, dynamic smoke pattern testing also confirms that the hood is properly situated and integrated into the room’s HVAC design. If the hood is moved to a different location—even four feet over within the same room—how it interacts with the HVAC will change; thus, requiring recertification.

If the hood is carefully moved for cleaning and then returned to its original location, recertification is not required. To ensure this occurs, some facilities place an X on the floor to mark the hood caster locations.

Q: What is the recommended frequency for cleaning the tops and the back of BSCs?

A: Cleaning the tops and the backs of the BSCs should be part of your monthly cleaning tasks.

Q: If the state requires that hoods be bolted to the wall as a safety precaution for earthquakes, how can proper cleaning be completed?

A: There are seismic restraints available that can be removed for the purpose of moving the hoods. Certifiers in those states can provide further information on properly accommodating the requirement while still being able to complete a thorough cleaning.

Q: Do you have any tips for keeping the sink area dry?

A: It is important to avoid any moisture buildup in the sink area. All too often, we see stacks of hand towels sitting on the countertop. In most cases, when the staff member retrieves the top wipe, the ones underneath become wet in the process, increasing the risk of contamination. Best practice is to install a wall-mounted, low-lint wiper dispenser wherein the wipers are pulled out from the bottom of the dispenser, thus reducing that risk.

Q: As the new USP <800> regulations specify the need for unpacking hazardous drugs in a neutral or negative pressure space, what airflow order should be followed in cleanroom design?

A: The hazardous drug (HD) storage room should be more negative than the HD buffer room, and the buffer room should only be negative to the anteroom. The only positive pressure room adjacent to the HD buffer room should be the anteroom because the anteroom will be as clean as the buffer room. The anteroom, in turn, is positive to the pharmacy, which is typically positive to the corridor.

Q: Do you recommend removing the diffuser screen for cleaning, and how often should this occur?

A: Yes, the diffuser screen must be removed for cleaning. Ideally, this should happen as part of the daily cleaning tasks, but at a bare minimum, it should be removed and cleaned weekly, which would be a marked improvement for those facilities that have never removed and cleaned the diffuser screen.

In some cases, however, the screen in front of the HEPA filter is not a diffuser screen but rather a protective screen mounted directly to the LAFW or in some cases, the HEPA filter. These protective screens typically cannot be removed.

Q: What is the risk of damaging the HEPA filter when removing a diffuser screen?

A: There is undoubtedly a chance that the HEPA filter could be torn or damaged when removing the diffuser screen. However, this must be evaluated in terms of the hierarchy of risk. Consider the risk from what could grow behind dirty diffuser screens over the course of 6 months versus the risk of damaging a filter.

Q: Is it acceptable to remove the return airflow grates to clean inside of them?

A: Because the return airflow grates are under negative pressure, they are not too much of a concern; however, any time there is visible contamination on the grate, I would recommend removing them for cleaning.

Q: How can we address pass-throughs that are not HEPA filtered to bring them into compliance with the FDA’s Insanitary Conditions at Compounding Facilities guidance?

A: First of all, HEPA filtered pass-throughs require a significant investment, and if your current pass-throughs require retrofitting, there will be additional construction costs. Typically, this means two retrofits, one for each buffer room. If this is cost-prohibitive for your organization, the first step I would recommend is to conduct testing to determine whether a contamination problem exists. The ingress/egress test that is used with isolators to determine if contamination is being introduced as items move into and then exit the isolator can also be applied to test the effectiveness of current pass-throughs. Additional environmental monitoring can be utilized as well. At the very least, this will provide you with hard data to either support your current approach or it will indicate the need for a change.

When designing a new facility, strong consideration should be given to adding HEPA-filtered pass-throughs. Of course, there is always the option to simply transfer materials through the anteroom, although that is not as efficient as using a pass-through.

James T. Wagner, principal of Controlled Environment Consulting, has over 40 years’ experience evaluating facilities and primary engineering controls used for aseptic processing. He has served on many industry-standard writing committees and was a member of the expert panel that revised USP Chapter <797>.


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