Seven Things You May be Forgetting When Cleaning Your Laminar Flow Hood

Laminar flow hoods are essential primary engineering controls (PECs) to prevent contamination of samples and/or products in laboratories, manufacturing facilities, hospitals, and compounding pharmacies. Maintaining cleanliness inside the hood with proper and regular cleanings is imperative to prevent cross-contamination, microbial contamination, and equipment malfunction. Though cleaning a laminar flow hood may seem straightforward, here are seven things to keep in mind:

1. Use lint-free cloths – After donning the appropriate clean personal protective equipment, gather all supplies needed to clean the hood including lint-free cloths or sterile gauze. Using lint-free cloths prevents the introduction of debris from the cloth itself into the laminar flow hood. Larger cloths can be folded into quarters, so that a clean piece of cloth can be used to clean each side of the hood. If working in a cleanroom environment, check that the chosen cloths are appropriate for cleanroom use.

2. Use compatible cleaning agents – In addition to using the lint-free cloths, be sure to use a cleaning agent that is compatible with the material composition of the hood. For example, bleach solutions are a common choice for cleaning and disinfection. However, bleach is corrosive and is not recommended for use in stainless steel hoods. If bleach must be used in a stainless-steel hood, great care must be taken to thoroughly rinse away all of the bleach residue using sterile water or 70% alcohol to reduce the chances of corrosion and prolong the life of the hood.

3. Never spray the inside of the hood directly – Laminar flow hoods contain filters, sensors, and electrical outlets that can be damaged when sprayed with cleaners. In hoods with grates, cleaner can pool below the grate and dry, which may damage the hood’s surface or leave a residue that is difficult to remove. Instead, spray cleaners onto the lint-free cloth or gauze until it is wet, but not dripping, or use an impregnated cleaning wipe.

4. Order matters – Inside hood surfaces should be cleaned in a particular order to prevent recontamination of clean surfaces. The ceiling of the hood should always be cleaned first, unless it is a vertical laminar flow hood that contains a filter on the ceiling. Exposed filters or filters with a grated protective shield should not be cleaned, as this could lead to damage. If the filters are covered by a solid (not grated) protective shield, the shield may be carefully cleaned; avoiding contact with the filter itself or excessive pressure. Starting in the back corner, wipe down the hood with the pre-wetted cloth or impregnated wipe using broad motions. Make sure each wipe motion overlaps the previous by about 25% to avoid missing any spots. Following the ceiling, grab a new cleaning cloth/wipe or unfold the cloth to expose a clean surface and clean the back of the hood, then each side, and finally the workspace. A new cloth or clean cloth surface should be used to clean each side of the hood. Always work your way from the back of the hood to the front and from the top to the bottom.

5. Do not over scrub – Harsh scrubbing can damage the protective layer on the surface of the hood and shorten the equipment life. Scrubbing can also introduce small scratches that are difficult to clean and disinfect. These scratches can become contaminated with microorganisms and act as a source of product contamination. Abrasive cloths or materials should never be used to clean a hood for similar reasons.

6. Remove residues – Some cleaners and/or disinfectants may leave behind a residue that coats the hood surfaces. These residues can build-up over time resulting in damage or discoloration, adherence of dust, debris, and microbes to hood surfaces, and/or protection of microbes from disinfection. Residues should be removed immediately after cleaning/disinfection. Cleaner and disinfectant residues are commonly removed with 70% isopropanol or sterile water followed by 70% isopropanol, if the cleaner/disinfectant is not soluble in alcohol.

7. Documentation – Laminar flow hoods should be cleaned on a regular schedule in accordance with applicable standards and written standard operating procedures (SOPs). To make sure you and your team maintain this schedule, each hood cleaning activity should be clearly documented. Be sure to include the date (and time, if necessary) the type of cleaning that was completed (wipe down v. deep clean) and any cleaning agents that were used. Clear documentation will also make it easier to plan ahead for deep cleans to make efficient use of time and workspace.

Keeping these seven points in mind when designing and executing hood cleaning SOPs will help keep your laminar flow hood functioning correctly and prolong equipment life. Proper and regular cleanings are necessary to prevent microbial and cross-contamination between procedures and users to ensure data and test results are reliable, promote safety, and maintain product quality and ISO, USP, and/or FDA compliance.