Commercial Mold Testing in Folsom PA: When the Air Sample and the Swab Disagree

In August 2026, I was called to a retail office suite on MacDade Boulevard in Folsom, Delaware County, after staff noticed discoloration on a wall in the back office. The property manager needed to know two things: what it was, and whether it was in the air the staff were breathing. Those are actually two separate questions, and this job answered them in a way that is worth walking through, because the two answers did not point the same direction.

An air grab sample was taken in the back office. A swab was taken directly of the discoloration on the wall. The air came back Normal. The swab came back positive for fungal growth. Both are correct results from the same room, taken the same day, and neither one is the whole story on its own.

1. The Discoloration on the Back-Office Wall

The mold was reported on a wall in the back office, an oval patch of discoloration visible against the wall surface. It was not extensive, and it was not the kind of finding that makes a dramatic photo, but it was clearly organic growth rather than a stain, and it was the reason the property manager called for testing in the first place.

2. Two Samples, Two Different Questions

I took an air grab sample of the back-office room air and a swab of the wall discoloration itself. These are not redundant tests. An air sample measures what is currently suspended in the air of that room, which is a proxy for what occupants are breathing. A swab measures whether the material at that specific spot is actively growing mold, regardless of whether it happens to be shedding spores into the air at that moment.

For a visible finding like this one, testing both ways is the right call rather than a formality. Skipping the swab and only testing air would have missed the growth on the wall entirely if the air happened to read Normal, which is what happened here.

3. The Lab Results: Normal Air, Fungal Growth on the Swab

The lab results came back split. The air sample from the back office was reported as Normal Mold, meaning the airborne spore count and profile were within the expected range for an indoor environment. The swab of the wall discoloration came back positive for fungal growth, confirming that the material itself was actively colonized.

This is not a contradiction, and it is not a lab error. Surface growth that has not been disturbed, or that is dry at the surface, does not automatically release spores into the room air in numbers an air grab will pick up. The wall was growing mold. The room air had not yet picked up an elevated count from it. Both facts were true on the same day in the same room, which is exactly why commercial mold and air quality testing is designed to check more than one thing when there is a visible finding to investigate.

4. What This Means for a Tenant or Property Manager

The practical lesson here is simple and worth repeating to anyone managing a commercial space: a Normal air result is good news, but it is not a green light to ignore visible discoloration on a wall. If this suite had only tested the air, the file would have closed clean while confirmed fungal growth sat untreated on an occupied wall. Testing both ways is what caught it.

My recommendation was to have a qualified mold remediation contractor further evaluate and remediate the wall to reduce the risk of a health hazard. Alongside that, the report addressed the conditions that let mold take hold in a commercial space to begin with: keep HVAC vents clean, add humidity control and HEPA filtration in occupied rooms, keep gutters and downspouts clean and properly aligned, maintain positive grade around the foundation, and trim vegetation back from the exterior walls. None of those items are dramatic on their own, but together they are what keeps a spot finding like this one from becoming a building-wide problem.

What Commercial Tenants in Folsom Should Expect From Mold Testing

This suite on MacDade Boulevard is a clean example of why sampling both air and surfaces matters whenever there is something visible to investigate. A Normal air reading and a positive swab from the same wall are not in conflict. They are measuring different things, and a property manager needs both answers to make a real decision. If you manage or occupy a commercial space in Folsom, Ridley Park, Prospect Park, or the surrounding Delaware County area and you have visible discoloration on a wall or ceiling, testing both the air and the surface is the way to get a complete answer rather than half of one.

Bob Klebanoff
Owner, All Seasons Home Inspections
610-348-6728  |  Free Estimate