Asbestos Clearance Certificates in Ontario: What O. Reg. 278/05 Actually Requires

A clearance certificate is not a letter of opinion. Under O. Reg. 278/05, clearance air testing after an indoor Type 3 asbestos operation is a prescribed procedure with a fixed numeric pass mark: every air sample must come back at or below 0.01 fibres per cubic centimetre of air. Until the work area passes, the barriers, the enclosure and the decontamination facility are not allowed to come down. This page sets out what the regulation prescribes, step by step, so an owner or property manager can tell a real clearance from a piece of paper.

We do the testing and we never do the abatement. That is the only reason a clearance result from us carries weight: we have nothing to gain from a pass. It is general information about the regulation, not legal advice.

The short answer

Clearance air testing sits in subsections 18(5) through 18(9) of O. Reg. 278/05. Section 18 is the section that prescribes measures and procedures for Type 3 operations, split between subsection 18(3) for outdoor work and subsection 18(4) for indoor work, with the operation itself classified as Type 3 under section 12. The sequence the regulation sets out runs in a fixed order, and skipping a step is what makes a certificate meaningless:

1. The abatement finishes and the work area, the inner surface of the enclosure, and the tools and equipment are cleaned by thorough washing or by HEPA vacuuming.
2. A competent worker inspects the area visually to confirm all visible dust, debris and residue that may contain asbestos has been removed. The Ministry's guidance points to ASTM E 1368-05 as a practice reference for that inspection.
3. The work area is allowed to dry.
4. A competent worker then carries out clearance air testing.
5. Only once the area has passed do the barriers, enclosure and decontamination facility come down.

Clearance is the last gate before people go back in, and the regulation puts it after the visual inspection for a reason: air testing a room that still has visible debris in it is testing the wrong thing.

The number that decides it: 0.01 fibres per cubic centimetre

The pass mark is not a judgment call. Under subsection 18(6), the work area inside the enclosure passes only if every air sample collected shows a concentration of asbestos fibres not exceeding 0.01 fibres per cubic centimetre of air. Not the average of the samples. Every one of them.

The same 0.01 f/cc threshold applies again where samples that failed a first phase contrast reading are put through a second analysis by electron microscopy. The number does not move; only the method does.

The two analytical methods the regulation names

O. Reg. 278/05 does not leave the lab method open. It names two, and which one is used changes what the sampling has to look like.

Phase contrast microscopy (PCM), under subsection 18(6). Analysis must follow NIOSH Method 7400, using its fibre counting rules. Sampling has to meet a set of prescribed conditions:

• Samples are taken inside the enclosure.
• Forced air must be used before and during sampling, so fibres are dislodged from all surfaces before the pumps start and are kept airborne throughout. This is the part most often skipped, and it is the part that makes the test meaningful. Sampling still air in a cleaned room will pass almost anything.
• At least 2,400 litres of air must be drawn through each sample filter.
• The number of samples must be as set out in Table 3 of the regulation, which scales with the size of the work area rather than being left to the sampler.

PCM counts fibres. It does not distinguish an asbestos fibre from a fibreglass or cellulose one, which is why a PCM failure is not automatically an asbestos failure.

Transmission electron microscopy (TEM), under subsection 18(7). Analysis must follow NIOSH Method 7402, and the sampling design is more demanding:

• Samples are taken inside the enclosure and outside the enclosure but inside the building.
• Forced air is required inside the enclosure, before and during sampling, on the same basis as PCM.
• At least 2,400 litres through each filter.
• At least five samples inside each enclosure and at least five samples outside it but inside the building.
• Inside and outside sampling must be done concurrently.

The paired inside and outside design is the point of TEM: it lets the analysis separate fibre that came from the work area from the building's ordinary background.

What happens when the area fails

A failure is not the end of the project, and the regulation says exactly what follows. If the work area fails, the prescribed cleaning steps are repeated, the area is allowed to dry, and a further test is carried out.

There is one branch. Where the first test using phase contrast microscopy has failed, the samples may instead be subjected to a second analysis using transmission electron microscopy rather than going straight back to a re-clean. That branch exists because PCM counts every fibre it sees. A room can fail a PCM count on non-asbestos fibre and pass a TEM analysis of the same filters, which distinguishes what the fibres actually are. On that second analysis the pass mark is still 0.01 f/cc on every sample.

A PCM fail followed by a TEM pass on the same samples is a legitimate, regulation-specified outcome, not a second opinion bought after a bad result. Knowing that is worth real money on a stalled site.

The exception worth knowing

Clearance air testing is not required in every case. Where the work has been done in a building that will be demolished and that will only be entered by workers involved in the asbestos abatement or by demolition workers, a competent worker is not required to carry out clearance air testing.

That exception is narrower than people assume. It turns on the building coming down and on who is allowed in afterwards. Where it does not apply, the enclosure stays up until the area passes. Where it does apply, the barriers, enclosures and decontamination facility still cannot be dismantled until they have been cleaned as the regulation prescribes.

Negative pressure, and why it belongs in the same conversation

While a Type 3 indoor enclosure is running, subsection 18(4) requires the enclosed area to be kept at a negative pressure of 0.02 inches of water relative to the area outside it. That is a containment requirement rather than a clearance one, but the two are connected in practice: an enclosure that lost negative pressure partway through the job is an enclosure that may have pushed fibre into occupied parts of the building, and a clean clearance sample inside the enclosure says nothing about that. On an occupied Ottawa building, an office tower on Albert Street or an apartment block in Sandy Hill where tenants stayed in place, that distinction is the one that matters to the owner.

Why an independent clearance is worth paying separately for

Nothing in the regulation says the clearance has to be carried out by someone other than the abatement contractor. It says a competent worker. The reason careful owners pay for it separately anyway is straightforward: the party that stands to be sent back to re-clean at its own cost is the party reading the result.

Because we do testing only and never bid abatement work, our result is that outside check. A pass from us is a pass. A fail from us costs us nothing, which is exactly why it is credible.

Ottawa specifics

Post-abatement clearance comes up here in a few recognisable situations. Federal and institutional properties across the core carry pre-1980 fireproofing and pipe insulation, and their abatements run as Type 3 enclosures with clearance as a contract deliverable. Pre-war housing stock in the Glebe, Centretown and Sandy Hill tends to produce clearance work after a flood or a fire, where a restoration contractor has had to open up walls containing older materials. And post-flood work in particular has a habit of turning into an urgent clearance: containment is up, the building is out of service, and every day the enclosure stays up costs money.

We work across Ottawa and the surrounding communities, including Kanata, Nepean, Orléans, Barrhaven, Gloucester and Stittsville. For post-abatement clearance we can usually sample same-day or next-day, because a standing enclosure is not a situation that waits.

Clearance sampling events typically run $400 to $800, depending on how many samples the work area requires under Table 3 and whether analysis is PCM or TEM. TEM costs more per sample and requires the paired inside and outside design above. The full pricing breakdown is on the cost page.

Related reading

• Asbestos air and clearance testing in Ottawa, the service itself
• Ontario asbestos regulations explained, including how Type 1, 2 and 3 are classified
• Designated Substances Survey, the survey that has to exist before the project starts
• Commercial and institutional testing

Common questions