How to Choose a Duct Cleaning Company

Duct cleaning has an awkward feature as a purchase: the work happens inside a sealed steel enclosure, overnight, while you are asleep. You cannot inspect the result the way you can inspect a painted wall.

That asymmetry is why the market has a wide quality range at similar prices. It is also why the sensible approach is to judge the things you can verify, rather than the things you are asked to take on trust.

We are obviously not a neutral party here. Read this as what we would want a client to ask us.

Start With the Credential You Can Actually Check

If your building has a compliance schedule, the certificate at the end has to come from an Independent Qualified Person registered with your council for SS9, mechanical ventilation or air conditioning systems.

Councils publish IQP registers. Look the company or person up before you engage them. It takes five minutes, it is free, and it is the only credential in this industry that is independently verified by someone other than the contractor.

Two things to confirm on the register: that they appear at all, and that they are listed for SS9 with your council. Registration is granted council by council and class by class. Registered in Auckland does not mean registered in Tauranga.

Note the distinction, because it is often blurred in sales conversations: a company can clean ductwork without being an IQP. Cleaning is maintenance, certifying is regulated. Plenty of cleaners are not IQPs, which is fine, as long as you know you will need somebody else for the certificate. Our post on IQP versus DIY unpacks that split.

The Questions That Separate Operators

What exactly is in scope?

Ask them to name the components. A complete kitchen extract job covers the canopy and plenum, the filters, the full duct run including risers and bends, and the extract fan housing and impeller.

The two most commonly excluded items are the fan and the sections of duct that are hard to reach. Both are also the dirtiest. If a quote is silent on the fan, that is not an oversight.

What happens where there is no access?

This is the question that tells you the most. Every system has a section that is awkward. The honest answer is either “we will install an access panel” or “we cannot reach that section and we will note it in the report”.

The answer you do not want is a confident assurance that access is never a problem. It is always a problem somewhere.

What do I get in writing?

You should get before and after photographs of each part of the system, a written report naming what was cleaned and what was found, and a note of anything needing attention.

One photo of a shiny canopy is marketing. Numbered access points, shot before and after, is evidence. Your IQP needs the second kind, and so does a council auditor or an insurer.

What standard are you cleaning to?

The answer should be bare metal. Not “significantly improved”. A residual film is fuel, and a fuel layer is the thing you are paying to remove.

What if you find something wrong?

A worn fan bearing, corroded ductwork, a missing fire damper. You want to know they will tell you, quote it separately, and not simply clean around it.

Insurance and health and safety?

Public liability cover, and a health and safety approach appropriate to working at height, in confined spaces, with electrical isolation and caustic chemicals. If they are going on your roof at 2am, this matters.

Warning Signs

• A firm price over the phone, sight unseen. Nobody can price a system they have not looked at. Either they are guessing, or the scope is narrow enough that it does not depend on your building.
• Claiming to certify without being on the register. Check. Every time.
• No mention of the fan. Covered above, and worth repeating.
• Reluctance to provide documentation. If photographs and a report are an optional extra, ask why.
• Cold call pressure and same day discounts. Legitimate operators in this trade are booked ahead, not chasing urgency.
• A price far below everyone else. Not automatically dishonest, but it almost always means a narrower scope. Find out what has been left out before you assume you have found a bargain.

Comparing Quotes That Are Not Comparable

The most common mistake is treating three quotes as three prices for the same job. They usually are not.

Put them side by side against these:

1. Is the full duct run included, or only the accessible sections?
2. Is the fan housing and impeller included?
3. Is documentation included, and what kind?
4. Is the 12A inspection included, or is that separate?
5. Are access panel installations included if needed, or extra?
6. Does the price assume after hours work, or is that a surcharge?

Once you have normalised for those, the prices usually converge considerably, and the cheap quote often turns out to be the expensive one. Our guide to what duct cleaning costs in NZ covers the underlying pricing factors, and what is included in a kitchen extract quote goes line by line.

Practical Fit

Beyond competence, a few things determine whether the relationship works.

• Will they work your hours? Most commercial kitchen cleaning happens overnight. A contractor who only works weekdays is not much use to a restaurant.
• Can they cover all your sites? Multi region operators should check IQP registration in each council, not just service coverage.
• Do they do both the clean and the certificate? Not essential, and some owners prefer them separate as a check. But one provider means one set of records and one conversation.
• Will they remind you? Compliance dates are easy to miss. A provider who tracks your anniversary and calls you is doing you a real service.

The Test That Matters Most

If you take one thing from this: ask to see the documentation from a job they did last month. Not a testimonial, not a case study. The actual report.

It will tell you immediately whether they photograph properly, whether they write up what they found, and whether they note the things they could not reach. A company that does those three things is almost certainly doing the cleaning properly too, because the discipline is the same.

To see how we approach it, read what a professional clean involves, or look at our kitchen extract cleaning and 12A inspection services.