Space heater safety, with the sources attached

The numbers, and where they come from

Almost every article you will read about space heater fires cites a percentage with no year attached, and the percentages have moved between report editions — which is how an undated statistic ends up circulating for a decade after it stopped being true. So here is the sourcing, in full.

The U.S. Fire Administration publishes two separate reports that between them answer the question. Heating Fires in Residential Buildings (2017–2019) records an annual average of 34,200 residential building heating fires, 165 deaths, 600 injuries and $367 million in property loss. Portable Heater Fires in Residential Buildings (2017–2019) records an annual average of 1,100 fires, 65 deaths, 150 injuries and $51 million in loss. Both are Topical Fire Report Series issues published in December 2021, drawn from the National Fire Incident Reporting System.

Divide one by the other and the shape of the problem is obvious: portable heaters are about 3% of heating fires and about 39% of heating fire deaths. That arithmetic is ours, from the two published annual averages, and we show it rather than quoting a rounded figure from a secondary source. The full page is here, with the per-year tables.

The three things that actually matter

1. 1.Three feet of clear space, in every direction. The USFA's own guidance is to keep anything that can burn at least 3 feet from every heat source. The leading factor contributing to ignition in heating fires is “misuse of material or product”, a category the report defines as including a heat source too close to combustibles.
2. 2.Plug it straight into the wall. A 1,500 W heater draws 12.5 A continuously — more than most extension cords are rated for, and cord failures happen at the connector where nobody is looking.
3. 3.Turn it off when you leave the room or go to bed. That is the USFA's wording, not a hedge of ours. Unattended equipment is a named contributing factor in the portable heater report, and it is the entire subject of our overnight page.

Certification marks, and what they are worth

A safety listing is the cheapest form of assurance available to you, and it is also the one most commonly faked in marketplace listings. UL and ETL are both marks of Nationally Recognized Testing Laboratories under the OSHA NRTL program, and for a portable room heater both mean the unit was tested to the same standard — UL 1278 for movable and wall- or ceiling-hung electric room heaters. Neither is “better”; a listing is a listing. The distinction that actually matters is explained here.

What you should be suspicious of is a listing page that shows a mark in a marketing image but never names a standard, a file number or a laboratory. On this site, every product's certification field either quotes what the manufacturer publishes or says plainly that no mark is published and you should check the rating plate. We do not assert a certification we could not find.

The circuit arithmetic nobody publishes

Here is a fact most heater articles never mention. A 1,500 W heater on 120 V draws 12.5 A. Electrical code treats a load running three hours or more as continuous and requires the circuit to be sized at 125% of it — which means a 15 A breaker supports 12 A continuous, not 15. 12.5 A does not fit on a 15 A circuit as a continuous load. It will usually run without tripping, which is precisely why nobody talks about it. The full working is here, along with what to do about it.