Pre-Clean Surveys: What to Expect

By the Duct Doctor team · Updated 30 October 2026

No two kitchen extract systems are the same. One might be a short duct straight out through a wall. Another might climb six floors through a riser, with fire dampers and an attenuator on the way. A pre-clean survey works out what you’ve actually got before anyone quotes or starts work. In doctor’s terms, it’s the diagnosis before the treatment. This guide explains what happens and what you get out of it.

Why a survey comes first

Quoting without a survey means guessing, and guesses tend to go wrong one way or the other. The quote might miss part of the system, or the team might turn up without the right access equipment. A survey avoids both. It also gives you an honest picture of the system’s condition before the clean, which is useful evidence later. If the system hasn’t been cleaned for a long time, the survey shows whether the first clean will take longer than usual, so there are no surprises on the night.

Photos and details, or a site visit

Some systems can be surveyed from photos and details you send. Useful information includes:

photos of the canopy, filters and any visible ductwork
where the duct goes, and where it comes out (roof, wall or riser)
photos of the extract fan and discharge, if they can be reached safely
your kitchen’s opening hours and cooking style
a copy of the last certificate and report, if you have one

Larger or more complex systems usually need a site visit, so the route of the duct, access panels and roof access can be checked in person.

What the survey looks at

The whole route of the system, from canopy to discharge.
Access panels: where they are, whether there are enough and whether they can be reached. See duct access panels explained.
Grease levels: readings at set points using a Wet Film Thickness Test (WFTT) or Deposit Thickness Test (DTT). See grease thickness testing explained.
The fan: type, condition and how it’s reached.
Fire dampers, attenuators and other in-line parts.
Working conditions: when the kitchen is closed, parking, roof access and any building rules.

Need it done? Duct Doctor cleans and tests kitchen extract and ventilation systems across London and the South East, with a certificate and photo report after every clean. Get a fixed quote.

What you get from it

After the survey you should receive a fixed quote that says clearly what will be cleaned, how and when. If extra access panels are needed, the quote should say where. If parts of the system can’t be reached even with new panels, you’ll know before the clean, not after.

Duct Doctor surveys every job first, from photos and details or a site visit, and a fixed quote usually follows within one working day. See our pre-clean surveys page.

After the clean

The survey is the starting point for the post-clean record. Readings and photos are taken again after the clean, so you can compare before and after. The certificate and report then list what was cleaned, any sections that weren’t accessible and the recommended next clean date. See post-clean verification and TR19 certificates explained.

Taking over a kitchen?

If you’re taking on a new lease or buying a business, a survey is a good way to check what you’re inheriting. Ask for the last certificate and report too. If there isn’t one, or it’s well out of date, plan a full clean before you start trading. See landlord and tenant responsibility.

Quick answers

Do I always need a site visit?

Not always. Smaller, simpler systems can often be surveyed from photos and details.

Will the survey find hidden grease?

Grease readings at access points give a good picture. Sections with no access can’t be measured and are noted.

Is the quote fixed?

Yes. Once the survey is done, you get a fixed price before any work starts.

Related services

More advice

This guide is general information. It isn’t legal or insurance advice: check your own policy wording and lease, and speak to a qualified adviser about your fire risk assessment.