Carbon monoxide leak check across Greater Hobart.

The post-Robinson background.

In 2010 Vanessa Robinson’s two sons died in Shepparton from carbon monoxide poisoning caused by a faulty open-flued gas heater in a tightly-sealed bedroom. The coronial inquiry identified that standard gas-heater services at the time did not test for the negative-pressure spillage condition that had developed in that house. AS 4575 was subsequently updated to mandate a specific spillage test under simulated worst-case exhaust conditions — rangehood on, bathroom fan on, clothes dryer running, doors closed. Every CO leak check we carry out follows that protocol.

The five-stage check.

1. Visual and ventilation assessment. Room volume, fixed ventilation openings, exhaust appliances inventoried, flue path traced, terminal location confirmed.
2. Baseline ambient CO reading. Calibrated electrochemical analyser, room CO ppm logged before the heater fires — rules out CO from any other source (e.g. attached garage, neighbouring chimney).
3. Heater fire-up + ambient logging. Heater fired on high setting, CO ppm logged at 10cm above the appliance and at occupant breathing zone over a 10-minute cycle.
4. Negative-pressure spillage test. Kitchen rangehood, bathroom exhaust and clothes dryer all switched on, internal doors closed. Smoke pencil at flue diverter to detect any spillage of combustion products back into the room.
5. Flue draft test. Manometer or smoke pencil at the flue draft hood, verify positive draft under all the negative-pressure conditions tested.

Pass / fail criteria.

• Ambient CO under 10 ppm sustained — pass.
• 10 to 30 ppm — pass with notes, retest at next service, investigate causes (burner fouling, flue restriction, room ventilation).
• 30 to 70 ppm — fail-soft. Appliance flagged for service before further use, written notification to occupant.
• Above 70 ppm sustained, or any positive spillage on the negative-pressure test — fail. Appliance isolated, gas service tagged off, immediate remediation required before re-use.

Why sealed-envelope Hobart homes are higher-risk.

The Vanessa Robinson scenario maps directly onto Hobart’s recent insulation, double-glazing and weather-sealing upgrades. Sandy Bay, Battery Point, South Hobart and North Hobart in particular have large numbers of pre-war and inter-war cottages that have been progressively sealed for thermal performance — but the original open-flued gas space heater is still bolted to the original fireplace. Each individual upgrade is correct in isolation; the cumulative effect is a house drawing far less make-up air than the heater was designed for, with the kitchen rangehood and bathroom fan generating enough negative pressure to reverse the flue draft. The AS 4575 spillage test is the only way to confirm this scenario hasn’t developed.

Symptoms that should trigger an immediate check.

• Headache or nausea that resolves when away from the home and returns when inside
• Drowsiness in a room with a gas heater running
• Yellow or wavering flame on a previously blue, stable pilot or burner
• Soot deposits around the heater casing or flue terminal
• Persistent condensation on windows in a room with a gas heater running
• A CO alarm sounding (if you have one fitted — we strongly recommend one)

CO alarms — recommended in every gas-heated Hobart home.

Standalone battery-operated CO alarms cost around $40–$80 and last 5–10 years before replacement. We recommend at least one in any room with an open-flued gas appliance, and one in the bedroom corridor of any home with a ducted gas system. They are not a substitute for an AS 4575 service but they are a critical backstop and they will alert overnight when the household is asleep.

Related services

The CO leak check is included in every annual gas heater service. If symptoms have appeared or a CO alarm has activated, book the leak check as a standalone urgent job. Where the underlying cause is flue spillage on an older flue, the flue and chimney inspection is the follow-on step.