The short answer: jobs fail clearance for a small number of predictable reasons — materials not fully dry, containment breached during the work, the HVAC system never addressed, or testing done too soon after disturbance. Get those right and passing is routine. The stage where most contractors lose a day is the final particulate knock-down, and that is where the choice between running scrubbers overnight and fogging a clearance treatment has real money in it.
What the assessor is checking
Visual inspection for remaining growth and remaining water-damaged material. Moisture readings to confirm materials are dry. Air samples compared against an outdoor control taken the same day. Sometimes surface sampling.
The outdoor control matters. Nobody expects a sterile interior — the benchmark is that inside looks like outside. Understanding that changes how you prepare, because you are aiming for parity rather than zero.
The four failures
1. Not dry
The most common. A structure that still reads wet will fail regardless of how clean it looks, and it fails on the moisture reading before sampling even matters. Document drying with meter readings over time rather than assuming.
2. Containment breached
A negative air machine that stopped, a poly wall that came loose, traffic in and out through an unmanaged opening. Particulate ends up in areas that were never part of the scope, and the assessor samples there. Then you are cleaning rooms you never billed for.
3. HVAC never addressed
If the system ran while mold was active, it moved particulate through the whole building and left some on the coils and in the ducts. Clean the work area, leave the ductwork, and the first cycle after you demobilise redistributes it. This is the single most common reason a job passes on one visit and fails on a retest.
Duct-Coil Klear covers coils and duct fogging for a home up to 2,000 sq ft on a gallon.
4. Testing too soon
Sampling immediately after HEPA vacuuming or moving contents catches particulate that is still airborne and would have settled. Let the space sit before the assessor arrives.
The clearance-stage decision
Once removal is done and you need the numbers down, there are two routes.
Run air scrubbers. No product cost, and a day of job duration you cannot bill. It addresses airborne particulate only — anything settled on surfaces or in contents stays settled.
Fog a clearance treatment. Product cost, a few hours, and it addresses surfaces and contents as well as air. PassKlear is blended for this specifically and is designed to be used in place of extended scrubber runtime.
On a job where a crew is standing by, the arithmetic usually favours fogging. On a job with schedule slack and tight material budgets, scrubbers are fine. The mistake is treating it as a religious question rather than a per-job calculation.
Coverage and pricing
For fogging plus contents, 5 gallons per 1,000 sq ft. For fogging only, 1 gallon per 1,000 sq ft. Product ships full strength, so there is no dilution step for a crew to get wrong.
A 2,000 sq ft residential job is roughly 10 gallons for a full treatment. Price that into the clearance line rather than absorbing it, and compare it against the labour cost of a day of machine runtime plus the demobilisation trip.
Bulk 55-gallon drums and dealer pricing are available if you are running volume.
A checklist for the day before
- Moisture readings documented and within normal range
- All water-damaged material removed, nothing deferred
- Containment intact through to the end of the work
- HEPA vacuum complete — walls and ceilings, not just floors
- HVAC addressed, filter replaced
- Clearance treatment applied and surfaces dry
- Space left undisturbed before sampling
- Assessor is independent of your company
Common questions
Why did my job fail clearance?
Most often materials that were not fully dry, a containment breach, an unaddressed HVAC system, or sampling too soon after disturbance.
Can fogging replace running air scrubbers?
At the clearance stage, frequently yes. During active demolition, no — containment and negative air are separate requirements.
How much product for a clearance treatment?
5 gallons per 1,000 sq ft including contents, or 1 gallon per 1,000 sq ft for fogging alone.
Should my company do the clearance testing?
No. Independent verification is worth more to the client and removes an obvious conflict.
See also: what clearance testing actually measures.
