Knowledge/Gas safety and CO/The ventilation rule changed on 31 March 2014
The ventilation rule changed on 31 March 2014
Check when the building was approved before you size anything. Approved before 31 March 2014, you need one cubic metre of room for every 3 megajoules per hour (MJ/h). Approved on or after that date, an open-flued appliance needs one cubic metre for every 0.4 MJ/h. Same appliance, seven and a half times the room.
- Before 31 Mar 2014
- 3 MJ/hper m³ of room, clause 6.4.5
- From 31 Mar 2014
- 0.4 MJ/hper m³, open-flued, clause 6.4.6
- Flueless, either way
- 3 MJ/hper m³ of room
- 30 MJ/h open-flued
- 10 or 75 m³depending on the date
What do the two clauses actually give you?
Both figures come from the Australian and New Zealand Standard AS/NZS 5601.1, as quoted in Energy Safe Victoria's (ESV) gas information sheet GIS 38. They look close on paper, but on the job they're miles apart. The standard writes them as MJ/h per cubic metre of room, so the smaller the number, the more room you need.
| Building approved | Clause | Flueless | Open-flued |
|---|---|---|---|
| Before 31 Mar 2014 | 6.4.5 | 3 MJ/h per m³ | 3 MJ/h per m³ |
| On or after 31 Mar 2014 | 6.4.6 | 3 MJ/h per m³ | 0.4 MJ/h per m³ |
So a 30 MJ/h open-flued heater in a post-2014 building wants 75 cubic metres. In a pre-2014 building the same heater wanted 10. That's the trap, and it's a date on a permit rather than anything you can see standing in the room.
A flueless appliance doesn't change. It's 3 MJ/h per m³ under both clauses, so the date only moves the number for open-flued.
How do you know which one applies?
You need the building approval date. Not the age of the kitchen, and not the age of the appliance. A 2019 heater in a 1970s house is sized on the 1970s approval. A reused heater in a 2016 build is sized on 2016.
If you can't find out the date, size it on the tighter clause. That's the cautious call, and it's the one you can defend.
Is getting the room volume right enough?
No. Getting the volume right doesn't prove the appliance is safe. A room can meet the clause on paper and still drop into negative pressure (air being pulled out faster than it can get back in) the moment somebody turns on a rangehood and shuts a door. That's what the negative pressure test is for, and it's the test that actually decides compliance.
If negative pressure is present, GIS 38 says the installation fails clause 6.3.1, no matter what the volume calculation said.
Found something on site you're not sure about?
Gas safety is the one area where the right answer and the comfortable answer aren't always the same, and you're the one holding the licence.
If you've got a job you're weighing up, Kevin's happy to talk it through.
Who this is for: small and medium HVAC contractors in Victoria. If you're a homeowner after a rebate or a repair, you need a licensed contractor, not us, and yours can point you the right way.
Related
- What to do when a customer won't fix an unsafe heaterFour steps in order, with the numbers to call. Notify the Building and Plumbing Commission properly and it won't take enforcement action against you.
- Every open-flued space heater under a Victorian alertSix heater families under a safety alert, with brands and phone numbers, the one you isolate instead of servicing, and what the 2022 sales ban caught.
- Sealing a house that still has an open-flued heaterRentals need draught proofing from 1 July 2027, and evap cooler vents are on the regulator's sealing list. Add an open-flued heater and that's a CO risk.
- How a negative pressure and carbon monoxide spillage test runsEnergy Safe Victoria's four-stage test from GIS 38, where the probe goes, why the pass mark isn't a ppm figure, and how to size the ventilation fix.
Review date: 1 March 2027. Figures in this area change without much notice and this page carries some that will go stale. Every number above is dated and sourced so you can check it yourself. If you find something out of date here, tell us and we will fix it.