My existing water heater is electric and is likely to need replacing soon. The heater is in a converted garage that I use as a guest room.

As the house is piped for gas, I'm considering the purchase of a gas water heater to replace the electric one. Is there any hazard with a modern gas water heater being used near where people are sleeping? (I'm more concerned here with fumes than the possibility of explosion.)

  • You might want to take a look at tankless water heaters (aka "on-demand" or "instantaneous" heaters). I'm not sure if they're any more or less safe carbon monoxide-wise, but I hear they're great. Commented Jul 28, 2010 at 22:32
  • @Jared - Someone else mentioned that to me as well, so I'm going to research those as well. Commented Jul 30, 2010 at 15:53
  • Sure, I wouldn't mind a large container of scalding hot water surrounded by FIRE in my bedroom closet.
    – spoulson
    Commented Aug 4, 2010 at 12:27
  • I sleep in the laundry room with a gas water heater and the only ventilation flow is a hole in the wall
    – Veronica
    Commented Jun 19, 2017 at 8:22

3 Answers 3


The amount of oxygen consumed by a hot water heater is negligible. The risk of the gas heater sucking all the oxygen out of the room is zero. Now that does not mean that it's code to have it in a bedroom, but there is no safety issue from consumption of oxygen.

The safety issue is on venting of the carbon monoxide (CO) from the hot water heater. In order to make the install safe, ensure that the new gas water heater is properly vented through the ceiling. There are lots of resources online about properly venting gas appliances. Here's a reasonable one to start with.

Obviously since a gas hot water heater requires adding a vent, it's more expensive to install. You may find that an electric water heater still makes financial sense once you consider installation costs.

As noted in the comments, be sure and get a CO detector for the room. These are relatively inexpensive and you can get them at your local hardware store or order through Amazon.

  • +1 for the reason they're usually banned. There was a case in Greece (or one of the Greek islands) a couple of years ago where the children in a family died due to faulty heater and CO poisoning.
    – ChrisF
    Commented Jul 28, 2010 at 20:58
  • 2
    Your answer is good, but missing one critical thing: make sure you have a CO detector! (probably on the other side of the room from the water heater)
    – gregmac
    Commented Jul 29, 2010 at 15:59
  • @gregmac, very good point. I added the CO detector to my answer.
    – JD Long
    Commented Aug 2, 2010 at 14:57
  • Can you provide a source for your statement that the amount of oxygen consumed by a hot water heater is negligible? I'm not trying to be a jerk but we are talking about something that can kill people here. Commented Aug 2, 2010 at 18:50
  • 2
    I know of no model code that allows a fuel burning water heater in a bedroom unless it is a direct vented type. Installing a CO detector anywhere there are fuel burning appliances is a good idea. But it is foolish to tempt fate by installing a fuel burning water heater in your bedroom, and relying only on a single electronic device to save your life. Don't risk it!
    – bcworkz
    Commented Jul 17, 2012 at 0:30

Pretty sure codes prevent using a gas appliance in a location where it will get it's combustion air from a bedroom. The reason for this is that if the heater is burning up all the oxygen in the room and it can't be replaced quickly enough through natural air flow through the house, you'd end up being asphyxiated in your sleep.

I think there's an exception though if you use a direct-vent model that gets it's combustion air from the outside. So you would need to make sure whatever hot water heater you buy is rated for that kind of installation.

  • 1
    +1. Triple check the regulations that apply and use a certified fitter.
    – ChrisF
    Commented Jul 28, 2010 at 20:29
  • Not too long ago several houses in the neighbourhood almost burned down because of a faulty part in one of those gas heaters.
    – txwikinger
    Commented Jul 28, 2010 at 20:40
  • wow, two downvotes on this? anyone care to comment why? Commented Jul 29, 2010 at 21:19
  • 1
    I'm not one of the downvotes, but looking at the first answer, maybe the disagree with the oxygen consumption logic?
    – derobert
    Commented Jul 29, 2010 at 21:54

CO is dangerous as it has not odor, It is best not to take risks.

You can place a gas water heater outside in a metal closet with the proper ventilation.

This is much safer. I also currently have an electric heater, but when I put in gas pipes a couple of years ago, I put one outside so one day I can set up a gas heater in a safe way.

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