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What are Electric Blankets?

Electric blankets have rheostats to control emperature.
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  • Written By: Michael Pollick
  • Edited By: Lindsay D.
  • Last Modified Date: 17 April 2014
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Electric blankets use grids of thin, insulated wires to generate heat internally. Earlier ones used adjustable thermostats to control temperature, but modern blankets (after 1984) use rheostats. Rheostats not only measure the heat generated by the blanket, but the body heat generated by the user as well. This results in a more even heating and fewer hot spots.

The history of these blankets is a little murky. When electricity was first introduced into households around the 1900s, would-be inventors added an electrical element to many common items. The first electric blankets were bulky and extremely dangerous. Most people saw them as curiosities, not legitimate consumer products. Few examples of early ones exist intact.

It wasn't until the 1920s that electric blankets became appealing to the general public. Tuberculosis patients would spend much of their recovery time outdoors in the fresh air, but the temperatures would drop overnight. Nurses began using these blankets to keep their patients warm while they remained outside. Eventually they made their way into the consumer market.

Electric blankets were actually more popular in the 1970s and 1980s, especially among the elderly and people with lower incomes. One thin one could take the place of several expensive cover sheets, insulating blankets and comforters. They could be placed on wheelchairs for added comfort. A hot-natured sleeper could adjust his blanket temperature without affecting his cold-natured spouse. Manufacturers touted many benefits of the blankets, but one serious drawback remained.

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Because the wires embedded in electric blankets are powered by electricity, there has always been a risk of shock or fire. Manufacturers routinely warn against misuse of the blankets, but consumers themselves cannot always detect compromised wiring. The continued use of older blankets has lead to significant problems with accidental fires and electrocutions. Many of the most dangerous models have already been recalled, but some elderly or low-income consumers continue to use the thermostat-controlled models sold in the 1980s.

There have also been suggestions that long-term exposure to electrical fields can lead to the development of cancer. Research in this area is still ongoing, but proponents of a cancer-free lifestyle suggest limiting the use of electric blankets. Alternatives do exist, including the use of heated waterbeds or modern insulated blankets that retain much more body heat. Consumers who do want to buy a newer model should look for a generous power cord length, an adjustable rheostat controller separate from the blanket, and detailed safety instructions. Those sold at thrift stores, flea markets and yard sales may be too old for safe usage.

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Discuss this Article

anon357862
Post 12

Years ago, literally 45 years ago, we received an electric blanket for Christmas. It actually broke my heart at the time, being a young wife with small kids. I couldn't relish the idea of not snuggling with my love all night, but we used it for probably a good thirty or more years before it seemed unwise as it was pretty darn old.

We then began the blanket period of piling the blankets on starting in the late fall. But it's still an issue of who is warm enough. So we just got a new electric blanket, which doesn't tell us what we can't recall, which is do we use other blankets w with this new one? Or will we be plenty comfortable with only one?

And it worries me a little that we had to buy one too big for our double bed, in order to have two controls. Will that be an issue? Thanks for any tips. --Anne

anon302634
Post 11

I firmly believe the amount of electromagnetic field we experience every day from televisions, radio waves, radar from police and weather far outweigh the electromagnetic field from the blanket.

anon227721
Post 10

I am interested in making my blanket stay on for 15 hours instead of the 10 hours that is the default setting. Does anyone have any ideas on how to do this?

anon166525
Post 9

We have had a Biddeford blanket for about 8 years (digital controller) and it recently stopped working. Being an engineer, I connected an oscilloscope to it and found that some wire has become intermittent at the blanket connector. I need to replace the cord (probably also the controller where the cord is attached).

Here is how this normally works: The controller sends 120 volts into a heating conductor that lets approximately 1.4 amperes flow. That wire is insulated and surrounded by a second wire made of a thermally sensitive alloy that has a resistance of 1000 ohms at room temperature. As the temperature of the sensing wire rises, its resistance increases and the controller shuts off power to the heating wire. The power is then cycled on and off to maintain the temperature. Due to this, the blanket does sense, at least partly, the effect of body heat. Should the insulation break down, the sensing wire will become "live" and the controller will shut off power.

As to cancer risks, the current is rather weak, the frequency is only 60 Hz, but the wire-to-body distance is short (440 mG at 1/4 inch). Science has raised questions but reached no clear answers yet about the effect of magnetic fields in the 2-833 milliGauss range at 60 Hz. My estimate is that an overnight electric blanket is not worse than spending 60 minutes daily near an electric cooking surface/toaster/microwave.

anon156174
Post 8

I just bought a Sunbeam queen sized electric blanket from Walmart that was marked down from $80 to $40 on clearance. I've had it plugged in and turned to "High" for over an hour, and it's not as hot as I had hoped. Yes, it's warm, but it's not hot, although I have to say the quality of the blanket is very good, and it does seem like it would last for many years.

anon123255
Post 6

About rheostats measuring blanket head and body heat.

That statement is total garbage. Rheostats don't measure anything. They vary their resistance proportionally to the turn of a dial. That's it -- look it up.

If there is a temperature sensing mechanism in "modern" electric blankets (big if), I challenge the writer to explain exactly how it measures the body heat generated, and how it controls blanket current as a result.

youbiKan
Post 5

I think that the key to enjoying a quality electric blanket is making sure that you dial in the proper setting for heat. Often if you simply select a random setting on most blankets you can either up entirely too warm or too cold. This can mean that the expensive blanket you bought is not doing its job.

You might have to adjust the settings a few times until you find the right one but for my personal preference I like to use something right in the middle, not too hot, not too cold. These settings can vary greatly between manufacturers of the blankets and care must be taken when experimenting as to not cause bodily harm. Some blankets are capable of heating up a very hot temperature and this can lead to skin burns if you fall asleep while the blanket is still heating up. Be sure to stay awake long enough to evaluate for yourself just how hot the blanket you use will become.

summertime
Post 4

The only thing that has discouraged me from ever purchasing an electric blanket is the very high cost if you desire a quality product. I take the general view when I purchase items that I want them to be quality and last much longer then the crap that is sold at department stores these days.

The quality Sunbeam electric blankets are very pricey and while I have heard good reviews from friends about it, I still have yet to see one go on sale. Perhaps the Spring time would be the right time of year to purchase an electric blanket as people will most likely be taking the extra bedding off at their homes.

dkarnowski
Post 3

Every year as the leaves turn in color and start to fall from the trees above, my wife puts on two types of electric blankets onto my bed. This is like laying down into a hot, dry, bath of warmth that allows me to sleep comfortably throughout the winter months.

While some people, as displayed in these comments, think that electric blankets are dangerous I can actually tell you that I have been using electric blankets for over twenty years and never have had an issue.

Besides an electric blanket on top of me while I sleep, my wife also puts an electric mattress pad on our bed. If you have never heard of this before I highly recommend that you explore the different options. Having both types of electric blankets on your bed means that you will stay warm from top and bottom. Nothing is more satisfying then getting into a bed that is warm all over.

GraniteChief
Post 2

Electric blankets are extremely dangerous and I highly recommend to anyone considering a purchase of one to reconsider. What you are essentially doing is covering you body with a shield of high current electrical fields. While the studies are still being done to determine if electric fields can cause cancer, why would you risk such great health hazard to you body.

I'll admit it, electric blankets are extremely effective at what they do and can be very comforting on cold nights but the fire risk associated with their use is just one more reason not to use them. Anytime you mix cloth and electricity there is potential for a fire and why someone would want to cover their body in a fire starting device is beyond my logic. Please be safe if you are one of the people out there that actually use electric blankets.

anon25664
Post 1

what is the approximate temperature for electrical blankets?

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