Laminar Flow Cleaning

I will go with second one, not to clean because i had an experience to see closely(metallic netting removed and all parts separated) how that HEPA filters look from inside.

Behind that metallic netting very fine delicate hepa filters are there that can damage even with a light pressure. So in my opinion if necessary (in case of spill etc.) you can clean it with light hand, but if not then one blower is there behind HEPA filter that will clean it automatically during time of stabilization.

it’s sensitive and can damage the hepa filters. No need to clean by yourself.

I don’t agree. I have been cleaning HEPA protective screens for years without issue and it is important to do so daily with a germicidal detergent and water followed by water daily because of drug overspray and other contamination. The key is not to get the filter behind the screen wet.

Best regards,

I understand the concern of deteriorating the HEPA filter. To me this all comes down to training the person who is going to clean the hood. In one of my previous hospitals the technician cleaning the hood used a spray bottle of alcohol to spray the metal grate. They didn’t realize that they were also spraying the the HEPA filter and they caused rapid deterioration of the HEPA filter and it needed to be replaced.

However, if the procedure is to wet a non-shedding cloth with water/sterile alcohol/germicidal detergent and then to wipe the grate there should be less likelihood of damage to the HEPA filter.

The key is to properly train the staff, and help explain why certain parts of the procedure are important.

Actually as per my previous experience if we clean directly the netted grate of the Laminar hood either with spray or wipe it will detoriate the hepa filter . And we need to replace .

As long as cleaning agents do not cross the screen onto HEPA, you should be ok with wiping using proper agents on non-shedding cloth. Training on proper procedure is key here.

I have been cleaning the filters for years without any problems.

I would like to clarify an early reply that are easing the screen with a germicidal detergent and water, sterile IPA needs to be used. Sorry for any confusion.

I was thinking about this topic a little bit more and I thought it might be helpful to share 2 other stories from my experience. To me they reinforce the importance of thoroughly cleaning the hoods and challenges with the current hood designs.

At one of the hospitals I worked at very early in my career I was told not to ever clean the metal grate that protects the HEPA filter. Initially, I just took the information and obeyed the command. After several months of working I started to notice all sorts of dried crud on the grate. I assume that it was from vials that were over pressured and then squirted their contents onto the grate. The stuff on the grate was there for months. Looking back on it now with our current understanding of bacterial or mold growth, if water can get on the grate then it’s possible for things to grow on the grate, therefore, it’s important to clean the grate. It’s also a very real concern that without careful cleaning, the HEPA filter can be damaged. Damaging the HEPA filter would be disastrous for your ability to maintain an ISO 5 environment in the hood, and potentially put your compounding operation at risk. I don’t actually see this as either you clean the grate and damage the HEPA filter or you leave the grate uncleaned and accept the risk of contamination growth. I believe you can train the people that will cleaning the hood to do so in a way that does not damage the HEPA filter.

Speaking about hood design, early on in my experience as a technician I noticed that there were parts of the hood that were not easy to access and thoroughly clean. On the vertical flow hoods that I worked with there is an air intake on the front of the hood to allow air to pass under the Direct Compounding Surface and recirculate the air. The problem was that the opening allowed for the collection of all sorts of dirt and unclean things. Because there was an area under the Direct Compounding Surface it wasn’t routinely looked at or cleaned. I can’t find the pictures right now, but I lifted up the Direct Compounding Surface and cleaned that space. It was disgusting. One could argue that the risk of contamination would be low since the air passing through that part of the hood still passes through a HEPA filter before it gets to the Direct Compounding Surface, but to me there are a lot of ways that the situation could be problematic. These experiences are why I’m much more in favor of designing a clean room without using hoods, but building the HEPA filters into the ceiling and using a more architectural solution to creating the clean room. All parts of the clean room are easy to see and easy to clean. To me, it’s a much more elegant design and solution.

Thank you for sharing these superb insights. I want to add my “ditto” here.

My microbiologist thought partner explained to me that after we spray our “disinfectant” liquids and they dry, many such commercial products leave a residue of organic compounds behind. It will be in a visible “crust” unless removed by (sterile) water or (sterile) alcohol – or better yet – sterile water allowed to thoroughly dry, followed by sterile alcohol allowed to thoroughly dry. He explained that the residual of disinfectants can be thought of as “germ food.”

You are correct in saying that we should never intentionally spray anything toward the delicate wonder that is our HEPA filter. Microbes of all variety and stages are ready to spring to life as soon as they are presented with the right conditions of oxygen, water (they’re microscopic by definition, so humidity matters), and organic nutrients. That’s why we call them, “germs.”

The every action and activity of every qualified operator relative to our equipment and environment should reflect this awareness. Training is absolutely key and must be universal and comprehensive.