Optional HEPA filtration on USP 800 exhaust

Optional HEPA filtration is a best practice design concept for USP <800> Nonsterile Compounding Rooms

(Transcript from Bryan Prince on The Pharmacy Inspection podcast – Listen to AUDIO here)

Hello to all of my compounding friends and colleagues and welcome to another episode of the Pharmacy Inspection Podcast.  Last week when Seth pulled me out of the mothballs and asked me to produce more podcast content because we had no idea the downloads were going to go through the roof, not because of anything earth shattering that Seth and I are discussing, but because of you the audience has decided that continuing education and idea sharing is super important, so I thank you and congratulate all of you in the compounding community of professionals for learning.

This idea of Learning and idea sharing brings me to this week’s story.  A few weeks back I spoke at an online conference where I discussed how to design and engineer a USP compliant laboratory.   One of the attendees sent me an email saying that their “USP 800 Expert” said you do not have to filter the exhaust air in a nonsterile negatively pressure hazardous drug room.  Their expert is correct, you do not have to HEPA filter or MERV filter or any other filter the air prior to externally venting it out of the building.

Quick sidebar, just a pet peeve of mine.  To all of my friends and colleagues in consulting, please stop calling yourself an “expert.”  An expert level anything implies that you perfected your profession and there is nothing else for you to learn.  We are all students of our profession and can learn something new every day or in my case on every project reveals something new, so for me, I’m a lifetime learner of the profession of construction, architecture, engineering, containment, USP compliance, and compounding. 

Back to the story where the expert said you do not have to filter air prior to externally venting the USP 800 hazardous drug negative pressure nonsterile room.  I used a lot of descriptive words there so we can compartmentalize exactly what we are talking about here.

There’s the letter of the law and the spirit of the law.  With USP chapters we get a little of both with the words “must” and “should.”  When we talk about compounding compliance and there are issues that are not addressed, like HEPA filtering the air prior to exhaust, then we should default to best practices.

In an earlier draft of USP chapter 800 there was mention of HEPA filtering the air prior to exhaust.  If you read the final 2019 version of the chapter you will notice no such language or reference exists on this topic.  The reason why is that on Table 2 the preferred method of handling the Containment Primary Engineering Control (C-PEC), e.g., the hood, is to externally vent it.  Having spent quite a few years in the containment business I can tell you that 90% of the Class-1 powder hoods manufactured in the market are equipped with HEPA filters on the exhaust side.  The other 10% of the hoods that do not have exhaust HEPAs are probably homemade from a local machine shop or someone got creative with glueing together plexiglass, which I really do not recommend. 

So, if the C-=PECs do have HEPA filters and are externally vented out of the building, then in theory the exhaust air going out to atmosphere is clean air.  This of course is assuming your certification company is actually performing a HEPA filter integrity test on your nonsterile powder hoods.

Now lets do some quick math on this powder hood.  If you have a small community pharmacy with a small nonsterile compounding room, say 10’ wide x 10’ deep and you design that room to the desired 12 air changes per hour, as defined in the chapter, then the powder hood with a 250 CFM exhaust is sufficient enough to achieve the 12 air changes per hour.

If your nonsterile compounding room is 15’ wide by 15’ deep then your one powder hood at 250 CFM is no sufficient enough to achieve the 12 air changes per hour, so you must also include either a low wall exhaust grill (which is best design practice) or a ceiling exhaust grille, which in my opinion is not best design practice.  Regardless, now both the C-PEC and C-SEC are externally exhausted.  The 150 to 200 CFM at the low wall exhaust grille is not necessarily filtered, so any airborne particulates in the room could be swept out through the grille and externally vented out of the building. 

Some of you may or may not be tracking with me on this principle, so let me tell you, nine out of ten pharmacies I have the pleasure of visiting has powder residue prevalent either on a door jamb, on the floor in a corner, or in the drawers or cabinets because I find it with my handy dandy UV flashlight.  The reason for that residue is compounding pharmacists and/or compounding technicians are consistently breaching containment, which is moving their hands in and out of the powder hood multiple times during the formulation process. This creates aerosolization of particulate into the air which again, may be swept out of the low wall exhaust grille and out of the building.  Hands are not the only point of aerosolization of particulate but I won’t walk through the exposure points of compounding workflow right now.

I pose this question to you our audience, and the experts.  Is it a good thing to send API drug particulate out of a building to be released into atmosphere.  I can hear the rebuttal now… The solution to pollution is dilution.  That’s an old saying and I’m going to step out here on a limb and say, that’s a terrible rebuttal.  Please do not send hormones or other drugs outside the building.  That’s not a local EPA conversation you ever want to have with regulatory agencies. 

 Without getting too overly long winded here please Design to best practice.  Just because USP chapters do not clearly define all of the rules of engagement doesn’t mean we can’t use some level of deductive reasoning.  Adding additional HEPA filtration prior to exhaust is a great idea and its kinda the right thing to do for our communities.  I realize this point can seem controversial, but that’s me, bad news Bryan in a nutshell.  I like the controversy, so please feel free to reach out to me if you ever have a question related to this content.  Since we are constant learners of the business and life, we welcome the discussion.