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  • Peg Minichiello

Microbial Testing: Your Guide When Working with Petri Dishes

When you’re running around your plant to make sure productivity stays high and your bottom line stays healthy, air testing may be the last thing on your mind. But according to the guidelines in ISO 8573-7 it’s an important part of your establishment’s tasks.

But compared to working with other equipment on site, working with a petri dish may seem quite foreign.

Don’t worry: we compiled a helpful guide to use when you test your compressed air’s quality. Remember these few tips and the process will go much smoother than usual.

Preparing to Take Samples

What you do before you start is as important as the sample itself. If you don’t take precautions you may inadvertently contaminate the sample:

- Wear gloves treated with alcohol to prevent dust or moisture from your hands to enter the sample.

- Wear a lab coat so your clothes don’t deposit dust or fibers.

- Protective eye gear protects your eyes, but also ensures mucus or tears don’t get into the dish.

- Wear a hair net and even a mask so loose hairs or a sneeze don’t ruin your testing procedure.

Throughout the sampling process you should limit contamination. Wiping your gloves with alcohol every few minutes or putting on new ones is a wise habit.

Working with the Petri Dish

The petri dish itself also has to be handled correctly to keep secondary contamination to a minimum. For example, while you’re not using the lid you must avoid dust settling on it by placing it down or storing it inside a sterile bag.

Only work with one dish at a time. Sealing the dishes afterwards is an ideal precaution and you can do this with a locking mechanism though not all plates have these. Simply make sure the lid won’t fall off when the sample is transported by taping down the plate.


Allow CDA Systems to take care of some of the rigors of working with compressed air. We know all about air testing and we can do installations or maintenance if you realize something’s amiss.

Talk to our experts about how we can help you: 925.667.3400/

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