Choosing a Viable Air Sampler For USP <797> Applications
As many sterile compounding pharmacies are looking to move to collecting their own viable air and surface samples, they will be in the market for a viable air sampler. The search for an air sampler can be overwhelming and you’ve probably asked yourself a few questions. “How do I know if it meets our needs? Why does it come with so many accessories? Do we even need them? Is the sampler any good? Why are they soooo expensive?” Now, I could just tell you which air sampler to buy. That would make things easy for you, but you wouldn’t learn anything. You really do need to know the whys and what to look for in an air sampler. There are quite a few things to consider when choosing an air sampler. Let’s run through them!
- Air samplers are like anything else out there, you get what you pay for. There are some less expensive samplers, but they do not have as good of a recovery efficiency as others, which brings us to…
- D50 value – Also known as cut off size. This is the size particle in microns that the sampler has a 50% chance of recovering. Basically you want to make sure the air sampler is going have a fast enough impaction speed that when the bugs hit the agar surface they stick, but not so fast that when they hit, they die. The manufacturer can provide this information.
- Disruption of air flow – ISO 14698 discusses the need for the air sampler used to NOT disrupt the airflow of the ISO device it is used in to sample. You want to look for something that expels the collected air down the body of the sampler and not out the side.
- Flow rate – It should NOT collect any faster that 200 liters per minute. There are some that collect 100 liters per minute, but then a 1000 liter sample will take you 10 minutes and that’s not really efficient when it comes to your time. Look for a sampler that falls in 180-200L/minute range.
- It must be able to sample 1000 liters of air.
- Physical aspects – It needs to be rugged. I’ve dropped air samplers and you want to make sure it’s not going to break. It also needs to be easily cleanable. Some also have autoclavable heads.
- Number of sampling heads – If you are only collecting samples with TSA (which is what I recommend) the air sampler only needs one head. However, there are samplers that have two (or even three) sampling heads, allowing you to collect multiple samples in one location at the same time.
- Calibration and maintenance – Some air samplers must be calibrated at every use, while others are calibrated once a year. Most have very manageable maintenance requirements.
- Equipment – Some companies offer tripods or disposable heads to go along with the sampler. They should also come with chargers.
- Media – Some air samplers require proprietary media. I would suggest you stay away from these samplers, because if media goes on backorder, you’re stuck. Some samplers use contact plates and some use petri dish sized plates. One is not better than the other. If you already are using contact plates for surface sampling and gloved fingertip sampling, choosing an air sampler that uses contact plates makes the most sense, but it’s totally up to you.
- Industry served – Look to buy your air sampler from a company that serves the aseptic manufacturing world. If their samplers are being used there, you can be assured they have gone through all of the proper testing and are reliable.
Still have questions about viable air samplers? Reach out to Pure Microbiology. Remember, best practice makes perfect.