A laminar flow hood (LFH) is a specialized workspace designed to provide a particle-free environment for sensitive procedures like cell culture, media preparation, or pharmaceutical compounding. This enclosure achieves its clean conditions by continuously filtering air through a High-Efficiency Particulate Air (HEPA) filter, which removes airborne contaminants and directs the flow in a smooth, non-turbulent, or laminar, pattern. Maintaining sterility within this workspace relies heavily on a structured and routine cleaning protocol. A systematic approach to cleaning ensures the hood consistently operates as a sterile barrier, protecting both the materials inside and the surrounding environment.
Essential Safety and Material Preparation
The cleaning process must begin with safety protocols to protect the worker and prevent the spread of contaminants. Before handling cleaning agents, personnel should don appropriate Personal Protective Equipment (PPE), including a laboratory coat, safety glasses, and cleanroom gloves. The selection of cleaning materials is equally important, with lint-free, non-shedding wipes being necessary to avoid introducing new particulate matter into the hood. Standard laboratory disinfectants, such as 70% isopropyl alcohol or 70% ethanol, are commonly used for general cleaning, as they are effective against microorganisms without leaving harmful residues.
The next preparatory step involves clearing the workspace of all equipment, samples, and materials. This removal ensures that every internal surface of the hood is accessible for thorough cleaning and disinfection. Once the workspace is empty, the fan or blower unit supplying the filtered air should be powered down. Allow the hood to sit undisturbed for a few minutes after the blower is off, letting any remaining air turbulence settle before the physical cleaning begins. The cleaning agent should never be sprayed directly onto the hood surfaces; instead, it must be applied to the lint-free wipe until it is saturated but not dripping.
Step-by-Step Surface Cleaning Procedure
The physical cleaning of the laminar flow hood requires a strict, sequential method to move contaminants out of the workspace rather than simply pushing them around. The process always starts with the cleanest area and progresses toward the area most prone to contamination, which is the work surface or deck.
Cleaning the Ceiling
The first area to be addressed is the hood’s ceiling or the filter screen, if it is accessible, using a new, disinfectant-saturated wipe. When cleaning the ceiling, the wiping motion should be linear, generally moving from the back of the hood toward the front.
Cleaning the Walls
A fresh, disinfectant-soaked wipe must be used for the next surface to prevent cross-contamination from the ceiling. The side walls should be cleaned next, using linear, overlapping strokes that move from the top of the wall to the bottom. This top-to-bottom motion ensures that any dislodged particles or cleaning residue travels downward, away from the previously cleaned upper surfaces. Following the side walls, the back wall of the hood should be cleaned using the same linear, overlapping technique, moving from the top edge downward.
Cleaning the Work Deck
The final surface is the work deck or floor of the hood, which accumulates the most contamination during use. Cleaning of the deck must proceed from the back edge toward the front opening, pushing any residual contaminants out of the sterile zone. The wiping motion should be in one direction, such as left-to-right, with each subsequent pass overlapping the previous one by about 25 to 50 percent. This technique prevents streaking and ensures the disinfectant is applied evenly across the entire surface. For effective disinfection, the agent must be allowed to remain wet on the surface for a predetermined contact time.
Post-Cleaning Verification and Restart
Once all internal surfaces have been physically cleaned and disinfected, the hood must be allowed to dry completely. This waiting period is necessary for the disinfectant to achieve its required contact time and for residual moisture to evaporate before the airflow is reinstated. After the surfaces are visibly dry, the fan or blower unit can be powered back on to restart the flow of filtered air.
A minimum stabilization period, known as the purge time, is required before the hood can be considered ready for sterile work. This purge time typically ranges between 15 and 30 minutes, allowing the newly generated laminar airflow to flush out any remaining airborne particulates that may have been introduced during the cleaning process. During this time, the hood should remain empty and undisturbed to ensure the environment reaches its required level of cleanliness. The final step in the procedure is to document the cleaning activity in a dedicated logbook, recording the date, time, and the specific cleaning agent used. This documentation provides a verifiable record of the hood’s sterile status for future reference.