Phoenix Journal · Ductwork
A trusted supplier list is your first line of defence against fire risk, failed audits and denied insurance claims. Here is how to vet, verify and keep the right maintenance partners on it.
Supplier management
A maintenance supplier list is only as strong as the questions you asked before a name ever went on it.
Most facilities teams inherit their supplier list rather than build it. A contractor did a decent job once, an invoice got paid, and the relationship quietly hardened into a habit. That is fine until the day something goes wrong - a failed insurance inspection, a grease fire, an enforcement visit - and you are asked to prove that the people maintaining your building were competent, certificated and doing the work to a recognised standard. At that point, a list built on habit tends to fall apart.
Building a list you can actually trust is a different exercise. It means treating every supplier as a compliance decision, not just a purchasing one. For safety-critical services such as kitchen extract cleaning, ventilation hygiene and local exhaust ventilation (LEV) testing, the standard you buy against is written down in black and white - and so is the paperwork your supplier owes you afterwards. This article walks through how to vet, verify and maintain that list so it holds up when it matters.
These three figures do more work than any brochure. They tell you what a genuinely competent supplier already knows and works to, so they double as a filter. A contractor who cannot tell you the interval for an LEV thorough examination and test, or who talks about kitchen extract cleaning without ever mentioning grease-deposit thresholds, has just told you where they sit on the competence scale.
The LEV figure comes from the Control of Substances Hazardous to Health Regulations. Regulation 9 requires most LEV systems to be thoroughly examined and tested by a competent person at least every fourteen months, following the method set out in the Health and Safety Executive's guidance document HSG258. Some higher-risk processes - welding fume and wood dust extraction among them - need testing far more often, typically every six months. The five-year record rule sits alongside it: the report is not a nicety, it is a document you must be able to hand to an inspector.
The 200 micron figure comes from TR19 Grease, the specification published by the Building Engineering Services Association (BESA) for cleaning kitchen extract systems. It sets the mean grease-deposit level your system must not exceed between cleans, with a clean expected to bring deposits back to well below that. Around seventy per cent of commercial kitchen fires start in grease-laden extract ductwork, which is why insurers and enforcing authorities treat this standard as non-negotiable.
Vetting a maintenance supplier is a layered exercise, and it pays to work through it in a fixed order every time. The first layer is safety pre-qualification. In the UK, that usually means a current SSIP assessment - Safety Schemes in Procurement is the umbrella body whose member schemes include CHAS, SafeContractor, SMAS Worksafe and the assessment bundled with Constructionline. A single valid membership tends to be enough, because SSIP's "Deem to Satisfy" mutual-recognition agreement lets one scheme accept another's assessment without a full reassessment. Ask for the certificate, check the expiry date, and note it in your records.
The second layer is trade competence specific to the work. General health-and-safety accreditation tells you a firm manages risk on site; it does not tell you they can clean a grease duct to TR19 or examine an LEV system to HSG258. For extract work, look for demonstrable BESA alignment and technicians trained to the current TR19 Grease specification. For LEV, confirm the examiner is genuinely competent in the HSE sense - the right combination of knowledge, experience and skill to judge system performance, not simply someone with a clipboard.
The third layer is the commercial and ethical due diligence that stops a supplier becoming a liability: adequate public liability and employer's liability cover, financial stability, and - increasingly expected on any serious approved list - anti-bribery and modern-slavery policies. Schemes such as SafeContractor already probe several of these, which is part of why buyers lean on them. Build a short, consistent checklist covering all three layers and apply it to every candidate. The consistency is the point: it is what turns a list of names into a defensible procurement decision.
That last point deserves emphasis. The single best predictor of a good supplier is the quality of the report they hand over. If you are choosing where to spend a stretched budget, this vetting discipline is exactly the sort of groundwork covered in our guide to prioritising building maintenance on a limited budget - safety-critical, legally required work earns its place near the top of the list.
Approval is the start of the relationship, not the end of your responsibility. A supplier list decays quietly - certificates lapse, key staff move on, standards drift - so it needs the same review rhythm you apply to the assets themselves. Set a calendar reminder against every SSIP and insurance expiry, and re-request evidence rather than assuming it is still valid. A name that sat on the list for three years without a single document refresh is a name you cannot really vouch for.
Verification of the actual work is where trusted suppliers separate themselves. For kitchen extract cleaning, TR19 Grease expects a full post-clean report, and you should insist on seeing it every visit. A compliant report includes before-and-after photographs taken from matching positions, Deposit Thickness Test or Wet Film Thickness Test readings confirming grease has been brought back below the required level, a written summary of the work done, notes on any access restrictions or areas that could not be reached, system drawings showing which sections were cleaned, and a hygiene certificate. If any of that is missing, the job is not finished - and your insurer may take the same view in the event of a claim.
For LEV, the equivalent is the thorough examination and test report: a clear statement of whether the system is performing as it should, the measurements behind that judgement, and any remedial actions. Keep every report on file for at least the statutory five years, indexed so you can produce it in minutes rather than days. This is also where a well-managed supplier list feeds naturally into a planned preventive maintenance programme, with cleaning and testing intervals set by usage - roughly quarterly for heavy-use kitchens, six-monthly for moderate use, annually for light use - rather than left to chance or memory.
Treat your best suppliers as partners in that programme. Share your schedule, flag changes in how a building is used, and let them tell you when an interval should tighten. A list built this way stops being an administrative burden and becomes a genuine asset - proof, on any given day, that the people maintaining your building are competent, certificated and working to the standards the law expects.
Questions
As a baseline, look for a current SSIP assessment - that means a valid membership of a Safety Schemes in Procurement member scheme such as CHAS, SafeContractor, SMAS Worksafe or the assessment within Constructionline. SSIP's mutual-recognition agreement means one valid scheme is usually enough. Beyond that, insist on trade-specific competence: TR19 Grease alignment for kitchen extract cleaning and HSG258 competence for LEV testing.
LEV systems must be thoroughly examined and tested at least every fourteen months under COSHH regulation 9, with some higher-risk processes needing testing every six months. Kitchen extract cleaning frequency follows usage under TR19 Grease - broadly quarterly for heavy-use kitchens running twelve hours or more a day, six-monthly for moderate use, and annually for light use. Your supplier should recommend intervals based on how your building is actually used.
For extract cleaning, expect a full TR19 Grease post-clean report: before-and-after photographs from matching positions, Deposit Thickness or Wet Film Thickness Test readings, a summary of works, notes on any inaccessible areas, system drawings and a hygiene certificate. For LEV, you should receive a thorough examination and test report confirming system performance. Keep LEV records for at least five years, as the law requires them to be produced on request.
Phoenix Duct Clean · by the numbers
Phoenix surveys and cleans kitchen and building ductwork to the TR19 standard - measured, cleaned and certificated, UK-wide.