During viable particle monitoring which sampling method is more effective - Passive air sampling or Active air sampling?

During viable particle monitoring we perform passive air sampling and active air sampling. Which sampling method is more effective during monitoring?

Actually both these methods are equally important. We can't say that a particular method is more effective. During viable particle monitoring all these methods are part of good environmental monitoring programme . This environment monitoring programme would be effective if all these methods are used together which will give us reliable data with respect to the count observed in a particular area. Both these methods have their own importance and we can't relay on only one method. Let's have a look on both these methods.

Settle plate or passive air sampling: In this method, SCDA media plates are exposed on different predefined locations for particular time like 4 hours as per EU GMP. During this time particles are settled down on the media plate by gravitational force. After that these plates are collected and incubated. Then cfu's observed after completion of incubation time. The limitation of this method is that the viable particles which are settled only on the media plate during that 4 hours of exposure time will be counted but the particles which didn't settle on the plate couldn't be observed. But good thing about this method is that, area could be monitored for long hours like we can cover the area by exposing the plates at 4 hours intervals.

Passive Air Sampling

        

              Passive Air Sampling

Volumetric air Sampling or active air sampling: This is one of the method we use during the environment monitoring. In this method we use the instrument which is called air sampler. That air sampler sucks the air forcefully and the impact of the air would be on the agar media plate. That's why this method is called active air sampling because we use any mode (air sampler) to sample the air from the environment.In this method we generally sample 1000 liters of air per location as per mentioned in guidelines. In this method sampling could be done in very short span of time depending upon the flow rate of the air sampler. For example if flow rate of air sampler is 100 liters/minute then it will take about 10 minutes to sample the 1000 liters air and if flow rate is 75 liters/minute then it will take 13.33 minutes to sample 1000 liters air. So, sampling time is depend upon the flow rate of the air sampler. In active air sampling we check the viable particles in the air by sampling the air rather than the waiting for the particles to settle down on media plates by gravitational force. But we can't use this method for long hours like it will take few minutes to sample the air and it will tell us the quality of air for that particular time of sampling. But how environment is behaving for long hours could not be detected by this method.

Active air sampling by using microbial air sampler

So, if we use both these methods then we can monitor the environment effectively for long hours by passive air sampling as well as by forcefully sucking air from the environment with air sampler to get reliable data.



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