Smoke Control & Stair Pressurisation Testing SWMS

Smoke control and stair pressurisation testing is high risk construction work in New South Wales because it is carried out on or near energised electrical installations during fire-mode testing, in or near confined spaces where ducts and plenums are entered, and at heights on roof fans, riser platforms and plant platforms. Section 291 of the Work Health and Safety Regulation 2025 (NSW) captures all three categories, and a safe work method statement is required under section 299. SafeWork NSW is the regulator. AS 1668.1 governs fire and smoke control in buildings and sets the door force limits the testing measures against.

**The mechanism that defines this work is that the plant answers to the fire alarm, not to the technician.** A smoke control fan is commanded by the building's fire detection system, and in fire mode it starts at full speed on a signal from anywhere in the building — a detector activation on a floor the crew has never visited, another contractor's dust, a test at the FIP by somebody who does not know the mechanical crew exists. A technician inside an AHU, at a fan, or in a duct is working on a machine that the building itself can start. **A control-system inhibit is not isolation.** The BMS is not isolation. An assurance that no test is scheduled is not isolation. The only isolation is electrical, at the fan's supply, locked and proved — and this document says so three separate ways because it is the point at which technicians are killed.

**Fire mode makes it worse, not better.** Smoke fans are designed to run to destruction in a fire: fire mode deliberately bypasses the thermal and overload trips that would otherwise protect a person or the machine. A fan in fire mode is a machine with its protections removed on purpose. And the testing does something to the building at the same time: for the duration of the test the smoke control system is **not protecting the occupants** — it is in test mode, its dampers driven, its interfaces inhibited — and the building is frequently full of people. Impairment planning, fire watch and full reinstatement are life-safety controls here, not paperwork.

Hazards identified

14 hazards covered, sorted by priority.

Control measures

Hierarchy-of-controls order: elimination → substitution → isolation → engineering → administrative → PPE.

1. 1**Isolate and lock out the fan's ELECTRICAL SUPPLY at its isolator before any person is at the fan, in the AHU or in the duct** — the fan answers to the building's fire detection system, and a signal from a floor the crew has never visited is a start command. Prove dead at the fan, make rotation physically impossible, and restrain the impeller where windmilling is credible because a windmilling smoke fan on a VSD generates at its terminals. **A control-system inhibit, a BMS point or an assurance that no test is scheduled is never accepted as isolation.**
2. 2Keep every person clear of the fan, its drive and its duct connections whenever fire mode is asserted — **in fire mode the thermal, overload and safety trips that would normally protect a person are bypassed by design, because a smoke fan is built to run to destruction in a fire.** Assert fire mode only under the documented test method with crew positions confirmed clear, and make no adjustment, inspection or measurement at the fan during fire-mode running.
3. 3Complete installation and pre-test verification dead under Part 4.7 Div 4 ss.154 & 157, carry out energised commissioning under a documented method with a competent person and a second person present who can isolate and rescue, and recognise that VSD-driven fans hold DC bus charge after isolation for the manufacturer's discharge period.
4. 4Obtain an arc flash risk assessment establishing incident energy and approach boundaries at the actual board, verify upstream protection, and close the door for any test that can be done closed.
5. 5**Isolate and lock the fan on the connected duct system before any entry — a duct is a confined space with a machine plumbed into it, and the fan's isolation belongs on the entry permit, not in a separate electrical conversation.** Block dampers in the entry path open so they cannot stroke closed on spring return behind an entrant, test the atmosphere before and continuously during entry, and provide a standby person who does not enter.
6. 6Plan the test as a formal fire system impairment with the building manager — **for the test's duration the system is not protecting the occupants, and the building is frequently full of people.** Limit the impairment to the systems and zones under test, stage testing so the whole building is never unprotected at once, provide a fire watch where required, and log the impairment with the facility and its monitoring service.
7. 7Work from fixed platforms, walkways and guardrailed roof areas where the building provides them, use an EWP or designed platform rather than ladders for two-handed work at fans and dampers, never stand on ducts or ceiling grids, and provide rated anchors with a rescue plan before any harness use.
8. 8Isolate and lock the fan's supply and prove rotation impossible before any guard is opened or any hand is at the impeller or drive, keep guards fitted for every running test, and prohibit loose clothing, lanyards and unrestrained hair at fans.
9. 9**Work to an override register that records every inhibit, force, isolation and mode change at the moment it is applied and requires each to be signed back** — a smoke control system left in test mode is a building whose fire response will not run. Prove the system back to automatic end-to-end by a detector- or FIP-initiated test rather than a switch position, and obtain the building manager's acknowledgement of reinstatement.
10. 10Isolate the actuator's power or air AND mechanically block the blades before any hand enters a damper — a spring-return actuator is a loaded mechanism whose purpose is to stroke the moment its signal is lost, and losing the signal is exactly what isolation does. Record the block's removal as a step before return to service.
11. 11Inform occupants which stairs are under test and control access during pressurised runs, measure door force to the method and limit in AS 1668.1 and record the results, verify relief and bypass arrangements where forces exceed the limit, and return stairs to normal operation between test runs.
12. 12Assess noise exposure against the exposure standard, take measurements from outside plant rooms where instrumentation allows, agree communication by radio or signal before hearing protection goes on, and select protection to the measured level to AS/NZS 1270.
13. 13Schedule occupied-area measurement with the building manager, barricade measurement positions, keep instruments and leads out of egress paths, and **never obstruct egress — a propped-open fire door or a blocked stair is an impairment in itself.**
14. 14Use the building's goods lift, trolleys and mechanical aids, stage equipment at the working level, lift fan motors and impellers mechanically, and use two-person handling for motors, actuators and ladders.

Applicable Codes of Practice

High-Risk Construction Work triggered

Worked example

A mechanical technician is inside a smoke spill duct on level 12 of an occupied office tower, inspecting a damper that failed to prove during commissioning. Before entering he put the fan into inhibit at the BMS workstation, and the building's fire panel technician — a different contractor, working a different scope — knows the mechanical crew is on site somewhere. On level 4, a fitout contractor sanding a bulkhead sets off a smoke detector. The fire detection system does exactly what it is designed to do: it commands the smoke control system to fire mode. The BMS inhibit is a software request to a building management system; the fire signal is a hardwired command to the fan's starter, and it does not pass through the BMS at all. The fan starts at full speed, in fire mode, with its overload and thermal trips bypassed by design, with a man in the duct. The investigation finds the inhibit worked perfectly — it inhibited the BMS. It had no authority over the path the fire system uses, which is the entire point of a fire system: it is built so that nothing in the building's ordinary control layer can stop it responding. The technician had isolated the layer that obeys people, and left connected the layer that obeys the fire. SafeWork NSW's position was that the SWMS treated 'isolation' and 'inhibit' as interchangeable words, and that a document written for fire-mode plant which does not state that the fire system bypasses the control system has not described the plant it covers. This SWMS says it in the scope, in the lead hazard row, and in the emergency section: **the fan answers to the fire alarm, not to the technician** — the isolation is electrical, at the fan's supply, locked and proved, and it belongs on the confined space entry permit alongside the atmosphere test.

Related legislation

• Work Health and Safety Act 2011 (NSW) — primary duty of care (s19), consultation (s47), notifiable incidents (ss35–38), industrial manslaughter (s26A)
• Work Health and Safety Regulation 2025 (NSW) — HRCW (s291), SWMS content and requirement (s299), SWMS review (s302)
• Work Health and Safety Regulation 2025 (NSW) — Part 4.3 Division 2 — confined spaces (ducts, plenums, smoke reservoirs)
• Work Health and Safety Regulation 2025 (NSW) — Part 4.7 Division 4, sections 154 and 157 — prohibition on energised electrical work
• Environmental Planning and Assessment Act 1979 (NSW) — annual fire safety statement obligations engaged by any system left impaired

Frequently asked questions