Cherney Blog: Inside The Petridish

Your blog resource for education, experience, and a good read!

Cherney Blog: Inside The Petridish

Your blog resource for education, experience, and a good read!

Best Sample-Best Result: EMP Sample Location

Posted by Matthew Fenske on May 18, 2020 3:37:20 PM

A while back as I talked with a manufacturer that was required by their customer to have an environmental monitoring program, they had expressed their confusion in their customer’s response when they shared their monitoring results. The manufacturer was proud to present 3 years’ (the entirety of their program) worth of data in which they never once had a positive result for the target bacteria. The manufacturer thought they had been doing an amazing job while their customer was less than confident with their results. The customer knew that given the manufacturers environment and required sanitation it was highly unlikely to never have a positive result, not because the manufacturer wasn’t taking care but, because of the ubiquitous nature of bacteria. Ultimately, the customer felt that the manufacturer was not sampling the most likely growth areas in their facility and was therefore missing the bacteria.

 So where is the best place to take environmental monitoring samples?


The story at the beginning of this blog was speaking largely about their experience in collecting surface samples but, it also important to have proper sampling locations for air and water as well.

For air sites there are a few key things to account for when selecting a site.

  • Find a site where your sampling equipment (petri-dish, petrifilm airs ampler, etc.) will not be disturbed by employees or equipment.
  • Sample air that is coming directly from outside into production areas.
  • Collect air samples near areas where product of concern is exposed to the manufacturing environment.

There are also a few important sites to test water at in your facilities.

  • Water should be collected throughout the year at any point that it is added as an ingredient or manufacturing aid.
  • Test recycled water such as that used in chillers and cooling systems.
  • Historically municipal water test results had been sufficient but, there is a current shift to have water tested where it enters your facility in lieu of the municipal results.

To clarify the confusion of the manufacture above, a key point to remember when sampling surfaces is your goal is to find the target organisms in the environment before it nears your product.

  • Split your sites up by zones and sample ~75% of your pathogen tests in zones 2 and 3 with the other 25% in zone 4. Test Zone 1 for indicator organisms.
    • Zone 1 = product contact
    • Zone 2 = adjacent to product contact
    • Zone 3 = typically within the production room away from product such as floors and walls
    • Zone 4 = outside the production room such as warehouses, break-rooms and offices.
  • Sample in hard to reach areas and those hard to clean.
  • Look for growth niches where there is moisture and/or product build up.
  • Look for chipping paint, rust and pitting on floors and walls.
  • Sample hollow bodied framework and around bolts.
  • Collect a representative sample from control panels
  • Look for areas where there is damaged equipment such as cracked plastic, worn rollers and shims.
  • Allow discretionary sites for your sampler to collect samples from areas that look out of normal condition such as excess grease, liquid on the floor or back up drains.

There are many other great areas to sample and so if you are reading this on social media, I invite you to leave some of those areas that you have found in the comments below.

Remember that rarely is the easiest sample to collect the best sample to collect.

Topics: Food Safety, Environmental Monitoring, Microbiology, Environmental Sampling, Integrity