Ambient Air Testing Options: Active or passive sampling
Many food, pharma, medical device, and packaging manufacturers are facing new requirements and regulations requiring the monitoring and testing of their ambient air quality in high-risk locations. Bodies like SQF, FDA, and ISO are often vague about what constitutes monitoring and what is required, pointing to the user to determine limits and frequency based on their individual risks. One of the most common questions we receive regarding ambient air testing is: should my facility choose to perform active or passive sampling? What are the benefits of each option? Though both passive and active sampling reveal bacteria, yeast, and mold contamination, they have pros and cons which must be carefully considered when constructing a monitoring plan for your client or facility. The ultimate goal of ambient air monitoring is to ensure that the air inside the facility is not a cause of contamination on the end-product. Air sampling, be it active or passive, gives invaluable information on the general environment in which your preparation is being manipulated (Cockcroft 2011).
Trace Analytics offers two forms of ambient air testing: active and passive. Active sampling is performed with an impaction sampler, the Trio.bas mono. This sampler draws in a specified amount of ambient air for the test. Passive sampling can be done in a number of ways, but at Trace Analytics, we perform this testing with settle plates. These plates are simply placed in a work location and left to rest for up to 4 hours. They collect any microorganisms that may fall on them during that time.
Passive Sampling: Settle Plates
Passive sampling with settle plates is a traditional method for sampling for microorganisms. Simply put, these plates are set out in a work area deemed high-risk through a thorough risk assessment. The plates should be out no longer than 4 hours as this can cause potential dehydration of the sampling media or create a film encapsulating the agar and preventing proper microbial growth.
Once the sampling is complete, the plates are wrapped in parafilm, labeled, and shipped back to the lab for incubation and analysis. Incubation times often range from 5-10 days depending on the specification you are trying to meet.
Passive sampling is inexpensive and simple to do because it doesn’t require any equipment. You can take tests in multiple locations all at the same time while work continues.
These results, however, are not quantitative as it is impossible to quantify the amount of air sampled with settle plates over that period of time. Your results will appear as CFUs (colony forming units) per plate on your reports.
Active Sampling: Impaction Sampler
Active sampling with an impaction sampler is an excellent way to extrapolate statistical data and receive quantifiable results. The impaction sampler draws in an exact amount of air onto the agar plate. The analyst can then determine results per cubic meter or foot depending on their requirements. Results with an active impaction sampler are qualitative and quantitative. They will be reported as CFUs per cubic meter.
Active sampling is much faster than settle plate testing – usually the samples take about 5 minutes. While the equipment is easy to use, Trace Analytics offers detailed instructions and step-by-step videos to help guide you through the sampling process.
When active sampling is performed, the user must purchase or rent the equipment. If purchased, the owner must maintain calibration documentation for the instrument. Trace Analytics helps facilitate these requirements. Our lab has a fleet of Trio.bas mono samplers that we maintain and calibrate annually.