Critical defects under AS 1851: what counts, who you must tell, and how fast

Of everything a fire technician writes on a service report, “critical defect” carries the most weight. It means part of a building’s fire protection won’t work if it’s needed, and from that moment the clock is running on who has been told, how, and what is being done about it.

AS 1851-2012 sets out exactly how defects are classified and how quickly each class has to be reported. Since 13 February 2026 that standard has been mandatory for Class 1b and Class 2 to 9 buildings in NSW, so the reporting rules are no longer just good practice there. They sit behind the building owner’s legal obligations, and behind your evidence that you did your part.

This guide covers the three classes AS 1851 uses, what tips a defect into “critical”, the notification timeframes, the owner’s obligations, how to manage an impairment until it’s fixed, the records that prove it all, and the mistakes that cause trouble later.

The three classes AS 1851 uses

Section 1.5.6 of AS 1851-2012 sorts everything found during routine service into three classifications, and clause 1.17.1 sets the reporting timeframe for each. Building Commission NSW summarises them in its good practice guide for AS 1851-2012:

There’s a fourth thing worth knowing about. A routine service activity performed outside the tolerance AS 1851 allows either side of its scheduled date is an “out of tolerance activity”. It is treated as a non-conformance, recorded in the logbook, and the service is carried out as soon as practical.

What makes a defect critical

The test is about the system, not the component. A broken part is critical when it leaves the system inoperable and that is reasonably likely to put occupants at significant risk in a fire. The same failed component can be critical in one building and non-critical in another, depending on what it does and what else protects that area.

Findings that are usually critical

• A sprinkler or hydrant system whose water supply has been isolated, for example a main stop valve found closed.
• A fire indicator panel that can’t warn occupants or can’t be reset.
• A fire pump that won’t start, or whose controller has been left in manual or off, so it can’t start on demand.
• A hydrant system that can’t maintain pressure or doesn’t perform as its approved design requires.
• Detection zones isolated and left isolated, leaving part of the building unmonitored.

Findings that usually aren’t

• A faulty component where the system as a whole still does its job (a damaged gauge, say, or a worn part that hasn’t stopped the system operating) is typically non-critical.
• Missing zone block plans, missing baseline data, a missing spare sprinkler cabinet or illegible labels are typically non-conformances.

Four findings, classified

These scenarios are illustrative (classification always depends on the building, the system and its approved design), but they show how the test works in practice.

A sprinkler main stop valve found closed

The valve set is fine, but the main stop valve on the incoming supply is shut, perhaps left closed after other trades worked on the building. Sprinklers with no water can’t control a fire, so the system is inoperable and occupants are exposed. That’s a critical defect. If you’re authorised and it’s safe to restore the valve, do it and retest, but the finding is still reported, because the building was unprotected for an unknown period and someone needs to find out why.

A fire pump controller left in manual

The pumpset is healthy, but the controller has been switched to manual, so the pump won’t start on falling pressure. The hydrant or sprinkler system it serves may not reach its design pressure in a fire. Treat it as critical, return it to automatic if there’s no legitimate reason for the isolation, and find out who changed it and when.

Several faulty detectors in one zone

Three smoke detectors in a basement car park fail their functional test. Whether that’s critical depends on coverage: if the rest of the zone and the building are still protected and the failures leave small gaps, it may be non-critical; if those detectors were the only detection in an area occupants rely on for early warning, it may well be critical. This is the kind of finding where recording your reasoning matters most.

No block plan at the valve set

The sprinkler system works, but there’s no block plan and no hydraulic data at the valve set. Nothing stops the system operating, but the information needed to verify its performance is missing. That’s a non-conformance: it’s reported within one week, with a recommendation, and a quote, to re-establish it.

Who you must tell, and how fast

Clause 1.17.1 puts the obligation on the technician, and the recipient is the “responsible entity”: the building owner or whoever the owner has nominated, such as a strata manager or facilities manager. Find out who that is before you’re standing in a pump room with a failed pumpset.

• Critical defects: tell the responsible entity before you leave site. If you genuinely can’t reach them, tell them as soon as possible. Then confirm it in writing within 24 hours of identifying it, and reconfirm it every time you find it again on a later visit.
• Non-critical defects and non-conformances: notify the responsible entity within one week. ACT Fire & Rescue’s guideline says in writing, and includes out of tolerance activities.

What a good written notice contains

• The building and address, the system, the asset and its exact location.
• What failed, the test or observation that showed it, and the result.
• The classification and a sentence on why it’s critical.
• When it was identified, and who was told verbally, when and how.
• The immediate risk and any interim measures you recommend.
• What rectification is needed, and whether you’re quoting it.
• Your name, company and a number to call.

Send a critical defect as its own notice. Buried on page 30 of a routine service report, it may technically have been reported, but nobody can say with a straight face that the owner was told.

State and territory extras

• NSW: AS 1851-2012 is mandatory for Class 1b and Class 2 to 9 buildings from 13 February 2026 under the Environmental Planning and Assessment (Development Certification and Fire Safety) Regulation 2021, and councils enforce it. Building Commission NSW lists penalties of $33,000 for individuals and $66,000 for corporations. Records must be kept on site for at least seven years. Separately, each measure in the Annual Fire Safety Statement has to be assessed as capable of performing to its standard, something a measure with an outstanding critical defect can’t honestly be.
• ACT: ACT Fire & Rescue’s guideline FSG-05 requires ACT Fire & Rescue to be notified in writing of all critical defects as soon as practicable after they’re identified, and maintenance records to be available to it within 48 hours of a request. ACT Fire & Rescue also says it will work with owners and contractors on realistic pathways to rectification, formalised through improvement notices.
• Victoria: owners must keep essential safety measures in a state that fulfils their purpose, and produce records of all inspections, testing and maintenance, including repairs, within 24 hours of a request from the municipal building surveyor or the chief officer of the fire brigade.
• Elsewhere: check your state or territory regulator. The AS 1851 classifications are the same everywhere; what the owner must do with them isn’t.

Rectification is the owner’s obligation

Contractors find and report defects; owners fix them. Building Commission NSW’s guide says the owner or responsible entity must review defect and non-conformance reports, undertake remedial or corrective action in a timely manner “guided by the seriousness of the defect”, keep servicing records in line with clause 1.16 of AS 1851-2012, and engage with their service provider to understand what the findings mean.

Timing follows severity. NSW’s legislation doesn’t require non-critical defects or non-conformances to be resolved immediately. They need a sensible plan. Critical defects are different: they need action as soon as possible, and something to manage the risk in the meantime. ACT Fire & Rescue puts it the same way: critical defects rectified with the minimum of delay, and the rest as soon as practicable.

Your job doesn’t end at the notice. Recommend the fix, quote it promptly, and make it easy for the owner to say yes. The faster a critical defect is closed, the shorter the window in which the building is exposed, and the less time you spend reconfirming it in writing on every visit.

Managing the impairment until it’s fixed

A critical defect means part of the building is unprotected right now. Something has to fill the gap until the repair is done, and the owner decides what that is, usually on advice from you, their fire safety practitioner and sometimes the fire brigade.

Building Commission NSW’s guide includes a case study worth reading: a lightning strike destroyed the fire indicator panel in a Class 2 residential high-rise. While repairs were arranged, the owners:

• contacted Fire and Rescue NSW;
• contacted their insurer and their legal adviser;
• told every resident that all fire safety systems other than the sprinklers were inoperative;
• engaged a security guard to patrol every floor between 6pm and 6am; and
• installed temporary manual fire fan controls.

The replacement went smoothly for reasons that had nothing to do with the emergency: the contractor held a copy of the panel program, the building had fire fan and full system matrices, and it had been through annual system interface testing. Good routine records made a bad day recoverable.

The records that prove you did your job

When something goes wrong, “we told them” is only worth what you can produce. Clause 1.16 of AS 1851-2012 sets out the records, and Building Commission NSW summarises them:

• Logbooks for each system, recording inspection and test results as pass or fail, referencing the relevant section of AS 1851-2012 and the interval, along with defects found and corrective action taken. A hard copy must be left on site at the end of every routine service.
• Tags and labels on hydrants, lay flat hoses, hose reels, extinguishers, fire blankets and passive fire and smoke assets, with a hard-copy summary record listing the equipment, the work done and anything missing or defective.
• Defect notices and rectification records: the written confirmations, and proof of what was done to close each defect.
• A yearly condition report (Appendix E of AS 1851-2012) consolidating the condition of every measure over the year.
• All of it kept for at least seven years and readily accessible to authorities and the owner.

Telling the client well

Nobody enjoys delivering bad news, and critical defects usually arrive with a cost attached. How you tell the client shapes whether the defect is fixed next week or next quarter.

• Lead with the risk, not the component. “If there’s a fire in the basement tonight, the sprinklers won’t get water” lands in a way a part number doesn’t.
• Be specific about what still works. Owners panic less, and decide better, when they know the scope of the problem.
• Offer interim measures, and be clear that choosing them is the owner’s call.
• Give them a price and a date quickly. A critical defect notice with no way to fix it just transfers anxiety.
• Put it in writing the same day, even after a good conversation.
• Stay factual if the client pushes back on the classification. Explain the definition, the evidence and your reasoning, and don’t reclassify to keep the peace.

Mistakes that cause trouble later

• Classifying a defect down to avoid an awkward conversation with the client.
• Leaving site without telling anyone about a critical defect.
• Burying the critical defect in the routine service report instead of sending it on its own.
• Not reconfirming an unresolved critical defect in writing on each later visit.
• Not knowing who the responsible entity is for a site.
• Closing a defect without retesting the system and recording the result.
• Letting a pile of non-critical defects sit until one of them becomes critical.

Building it into your workflow

1. Record the responsible entity and a backup contact for every site before the first visit.
2. Classify on site with the three definitions in front of the technician, and capture why.
3. For a critical defect, notify verbally before leaving and log who was told, when and how.
4. Send the written confirmation the same day. A template makes this take two minutes.
5. Track every defect to closure: quote, approval, rectification, retest, closed.
6. Reconfirm open critical defects in writing each time you find them again.
7. Roll everything up into the yearly condition report.

Frequently asked questions

Who decides whether a defect is critical?

The competent person carrying out the routine service classifies it on site, against the AS 1851 definitions. Owners and their fire safety practitioners can question a classification, which is exactly why you record your reasoning.

Does the 24-hour rule apply to every defect?

No. Written confirmation within 24 hours applies to critical defects. Non-critical defects and non-conformances must be notified within one week.

Do non-critical defects have to be fixed straight away?

Not in NSW. The legislation doesn’t require non-critical defects or non-conformances to be resolved immediately. They do need a plan, because left alone some will become critical.

What if the owner won’t pay to fix a critical defect?

Keep telling them in writing, every time you find it, and keep the records. In the ACT the fire brigade must be notified of critical defects regardless. You can’t fix the building for them, but you can make sure nobody can say they weren’t told.

Do we have to tell the fire brigade?

In the ACT, yes: ACT Fire & Rescue must be notified in writing of all critical defects as soon as practicable. Elsewhere the AS 1851 obligation is to notify the responsible entity; check your state’s rules. Owners may still choose to contact the brigade as part of managing an impairment, as the owners in the NSW case study did.

Is missing baseline data a critical defect?

Normally not. Missing baseline data is recorded and reported as a non-conformance, and the routine service is still carried out.

We fixed it on the spot. Do we still report it?

Yes. Record the defect, the repair and the retest result. If the building was without protection while you worked, the owner still needed to know.

Sources and further reading

• Good practice guide for the inspection, testing, maintenance and repair of fire protection systems in NSW buildings, Building Commission NSW (January 2026)
• Building fire safety requirements under AS 1851-2012 (Building Commission NSW)
• Responsibilities of building owners under AS 1851-2012 (Building Commission NSW)
• FSG-05 Maintenance of fire protection systems and equipment, ACT Fire & Rescue (August 2023)