Peter Sawchuck with Consumer Reports used one test to assess whether the overheat sensor shuts the heater off before it poses a fire risk.
With the Optimus space heater, the sensor did not activate in time. The test fabric caught fire in a matter of minutes.
The Optimus heater also failed a second test in which a folded cloth that simulates a drape was placed on it. Like most heaters, the Optimus carries a warning that states: "Risk of fire - keep combustible materials, such as furniture, paper, clothes and curtains at least three feet away."
"Drapes and fabrics can easily contact any heater in a typical home. And this one was the only electric heater to ignite the fabric in our test," he said.
Because of the potential risk of fire, Consumer Reports judges the Optimus model H-5210 heater a don't-buy, due to a safety risk.
Consumer Reports also uses an infrared sensor to measure surface temperatures. The bar on the Sunbeam space heater model SQH310 gets hot enough that it could burn you if you grab it.
Other tests measured performance in a chamber outfitted with temperature sensors. Testers measure how quickly each heater can comfortably warm a room. In the end, Consumer Reports named the $40 Holmes portable heater model HFH436 a best buy. It passed all of Consumer Reports' safety tests and can quickly heat up a room.
Consumer reports contacted Optimus and test results the company provided show a potential safety problem with the H-5210 heater. A spokesperson says the company fixed the models made in 2012.
The heaters Consumer Reports tested -- 2011 models -- were purchased this past summer. Consumer Reports is asking the Consumer Product Safety Commission to recall the Optimus H-5210. It urges anyone who owns the heater made in 2011 or earlier to stop using it and ask the retailer for a refund.