Sampling Times For Air O Cells

I have a friend in another state who usually runs the pump for just 5 min when using Air-O's.

He says that's all that is necessary.

I have always run them for 10 min.

Russ H., and other experts, what say you?

It's been a while since i have done any but i remember 15 ltr for 5 minutes

15 liters per minute for 10 minutes

What he's referring to Pete is a product from Zefon International that requires only 5 minutes. It is a legitimate test, we can analyze those at InspectorLab, but it's our position that the Air-O-Cells you are using are better. When you run the pump longer across a media that collects for longer, the test is more accurate.

Nathan wrote:What he's referring to Pete is a product from Zefon International that requires only 5 minutes. It is a legitimate test, we can analyze those at InspectorLab, but it's our position that the Air-O-Cells you are using are better. When you run the pump longer across a media that collects for longer, the test is more accurate.

No. I am specifically talking about Air O Cells which are rated for 15 lpm and 10 min.

He only runs them for 5 min.

The cut point for the AOC (the point at which 50% of the size range of spores you are trying to capture are captured that enter the impactor) is rated for a flow rate or 15L at 10 minutes.

Any variation of that must be justified by what you, a priori, decide is best for the environment you are sampling. That is, the flow rate is the same, so the impaction efficiencies should remain stable, but the amount of time you have to capture spores is cut in half. Thus, you are not going to model the environment as well as it could be.

Of course, more time is even better, but the chance for overloading and warping the soft impaction media go up. Again, there is no a priori way to anticipate this.

The short sampling time is meant to limit the amount of debris that is impacted on the media and therefore, give the analyst a better chance to identify and count the spores accurately.

When too much debris is impacted, two possibilities exist:
1) debris is impacted and there is no longer a surface for the spores to impact

and/or

2) the spores are impacted and the debris covers the spores so they cannot be counted or identified.

With increasing debris load, there is an increasing inaccuracy of the counts. We note that on our reports in the “comments” section on the bottom of page #2.

There are labs out there that used to recommend outside samples be taken at 15L for 5 minutes, but that is a guess by them. Often outside samples are overload with debris. We haven’t seen a big problem with overloading of outside samples.

Overloading of samples most often happen inside when there are lots of skin cells in the air (no way of knowing beforehand if this will be the case), or maybe more often, when there lots of drywall dust is in the air. The drywall mostly is when construction is going on or remediation.

Inspectors must take great care not to contaminate the AOCs with the dust from their hands. They should wash or wet wipe them down if they are doing a sample after the inspection or when they have touched something dusty. The AOCs are electrostatic and they will draw dust to them like crazy.

So in other words Pete, whoever you're referring to is either cutting their time or is dealing with some damn dirty houses to be unscientific about it.