Fire in Microwave

Page 1 of 2  
A friend put a couple of 'fast food' hamburgers in her microwave to warm them but forgot they were wrapped in aluminum foil. When she saw the ensuing fire she turned off the microwave and kept the door closed until the brief fire burned itself out.
The microwave seems to operate normally but she swears it cooks hotter than before the fire. In other words it doesn't take as long to heat things in the microwave. Does this make sense to anyone? If it does, what kind of repair would be needed to make it right again.
Thanks for any help.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I doubt very much that there was any serious damage other than a chance of some burning to the inside paint that were in contact to any flame (if so), or some smoke coating in the passage of the air flow.
The damage to the paint is not serious. The smoke coating, if any is there, may make the oven smell for a while being used, until it works it way out.
You could have it properly cleaned and checked out in a service centre to be sure of its performance and safety. I would strongly advise you to not do any maintenance on the microwave oven yourself.
As for cooking faster, I doubt it very much. I think that in the fear of the event, she has the wrong perception.
Never put any metal of any kind in a microwave oven. Arching or flame can occur. Use only containers that are microwave oven approved. Some plastics that are not rated for microwave cooking may start to melt or burn, can release dangerous fumes, and also contaminate the food. If you use any glassware or porcelain ware in the microwave oven, make sure that it is rated for microwave ovens.
When cooking any foods in the microwave oven, make sure that they are properly vented in their containers. Foods that can be sealed by their skin, such as apples, pears, and various fruits, potatoes, must be punctured. Eggs must have their shell broken, and the yoke membrane must be punctured. If not, these types of foods can explode, thus causing damage, and or a big mess.
--

Jerry G.
=====


"Newby" < snipped-for-privacy@nowhere.net> wrote in message
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

What the fuck are you talking about? My microwave oven has a metal rack in it. The interior of the oven is MADE of metal.
Metal is OK in a microwave.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Oscar_Lives wrote:

depends.........
http://www.gallawa.com/microtech/metal_arc.html
ALso, stupid microwave tricks: http://www.amasci.com/weird/microexp.html
Bob
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

can
in
One of my current microwaves has metal racks, the other glass. Some microwaves will spark with metal, some will not.
Take a CD, and nuke it for TWO seconds. Watch it. It is pretty, and the CD looks cool. BTW, don't use a CD you ever intend on playing again.
Steve
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Oscar_Lives wrote:

I suggest you try it in your microwave. Try some crumpled up aluminum foil, or get a bunch of nails and put them in a cup to hold them.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Oscar_Lives wrote:

It depends on the design of the rack, spacing of the wire etc.
--
Joseph E. Meehan

26 + 6 = 1 It's Irish Math
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I think you should be more respectful when shooting off your mouth (fingers) on the keyboard. You have no idea of the qualifications or background of the person you are commenting to. Maybe it can be someone who is a specialist, and has worked in the design of these things!
I think you should have respect for others. You should have asked about why you can put a metal rack in some microwave ovens, and not put someone down because of your pure ignorance!
The only reason I am answering this, is because there are many others who have some respect, and would be interested in the answer.
If you were educated in the field of physics, mechanics, or electronics, you would realize that there is something called resonance. Microwave ovens work in a particular frequency band, and therefore metal objects can be designed to not react to the frequency used in the oven. The metal cavity that the oven is constructed with, is invisible to the RF (Radio Frequency) energy being emitted from the magnetron. This metal cavity is actually a non terminated waveguide, and thus anything that is out of the exact resonance will become a load to it, and be heated up. The metal rack is designed in size and in the way it is formed to act as a near zero load to the wavelength (frequency) used. Even the paint used inside of the microwave oven must have specific characteristics. Because the cavity of the microwave oven is non terminated, is reason why the magnetron can be easily damaged if the oven is used without cooking something inside. Even the location and type of lamp used for the illumination in the microwave oven is critical.
The standard frequency used in the home cooking microwave oven is 2.45 gHz. This frequency was not pulled from rolling dice. There are a number of reasons for this choice.
Radio waves in this frequency range have a particular property where they are absorbed by water, sugars, and fats. When they are absorbed they are converted directly into heat by inducing accelerated vibration of the molecules. Microwaves in this frequency range have another interesting property. They are not absorbed by most plastics, glass, or ceramics.
Only the molecules that are being excited are heated up. This way non reacting containers will not heat up. The container of the food being cooked will only heat up by conduction from the heated food inside.
Metal reflects microwaves, which is why metal pans do not work well in a microwave oven, and can even cause damage to the magnetron by overloading it. Under some conditions, metal can conduct the microwaves and act as an induced conductor, thus converting the energy back to electricity. This is the reason why some metal object will cause sparks, and even make things catch on fire. The only exception to this is if the metal object can be in resonance to the wavelength to not be seen as a load.
There are industrial microwave type ovens that are working at other frequencies. These are used for drying specialized epoxies, curing plastics, and many other applications. There are also microwave dryers used in some types of fabric manufacturing processes. Some of these are working down at 1.5 gHz, and others are working up to about 3.5 gHz, depending on the application. These will not be good for cooking foods.
If you have one of these 2.4 gHz telephones it is normal that when you go near to your microwave oven while it is working, the phone may be interfered with. This not dangerous. There is a slight amount of energy leakage from all microwave ovens. There are specifications for this leakage. It must not exceed a particular amount.
The limit in most countries is 5 milliwatts of microwave radiation per square centimetre at approximately 2 inches from the oven surface. This is far below the level known to harm people. As you move away from an oven, the level of any leaking microwave radiation that might be reaching you decreases dramatically. For example, someone standing 20 inches from an oven would receive approximately one one-hundredth of the amount of microwaves re ceived at 2 inches. The energy drop-off works according to the inverse-square-law factor. Go to http://www.fda.gov/cdrh/consumer/microwave.html for more details about microwave oven safety and applications.
We recommend that children and pregnant women should walk away from the microwave oven while it is working. We recommend about 6 to 10 feet. This will dramatically reduce any risk of radiation absorption. There have been many studies about low level radiation from microwave ovens, TV sets, monitors, and other home appliances. There have not been anything conclusive as of yet, so it is better to not take any chances. It is known that over certain intensities, electromagnetic and RF radiation is dangerous, and will cause cancer, and other types of biological damage. The dangerous intensity level will be different at different frequencies. This is a complex field in itself. Caution is the best advice. Harmful radiation is not able to be felt, unless it is very intense. The effect of this radiation can be accumulative if the exposer is frequent.
If you want to be very safe, you should have your microwave oven checked at least once a year. The door seal and hinges can wear out. This is the greatest weakness in microwave ovens. It only takes a few thousandths of an inch of extra space to allow higher radiation leakage. The service centres that service microwave ovens should have the proper instrument to measure the microwave radiation. Some places will not charge to take the measurement. Others may charge a few dollars for the technician's time. If there is leakage, this can usually be easily repaired. Sometimes it is just the hinge adjustments, or replacing some simple parts.
We do not recommend that the consumer attempt to service his own microwave oven. It is the most dangerous appliance in the home if it is not used properly, or is opened up. The TV set and computer monitor is the second runner up to this.
--

Jerry G.
=====


"Oscar_Lives" < snipped-for-privacy@nospam.net> wrote in message
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

can
in
Now you change your story? You just said: "Never put any metal of any kind in a microwave oven."
Which is it?
Never put ANY metal of ANY KIND vs. Metal is OK?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Oscar_Lives wrote:

My goodness you ARE a fool. Learned how to read but never how to think? Never put metal in a microwave that didn't COME WITH the microwave. Metal rack specially designed for a particular microwave will not cause problems with that particular microwave. Other metal WILL. Clear enough? Need a map? Idiot!
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

There is nothing special about the metal rack in a microwave, it is just insulated against touching the cavity walls and door.
You can use *limited amounts* of metal in a microwave provided:
1. It is not touching the cavity wall or door (or damage will occur to those surfaces).
2. There are no 2 metal surfaces touching or close to one another (or arcing will occur).
3. There is still enough uncovered food inside the unit to absorb the microwaves produced so they do not feed back to the magnetron tube and damage it.
4. You keep in mind anything covered by metal foil, etc. will not be heated.
Number 4 is handy if you're cooking something like a turkey or chicken leg where you don't want the end with little or no meat on it, heated.
You should also never use gold or other metal inlay plates in a microwave as that inlay is rarely continuous and any breaks in it will cause arcing, resulting in damage to the plate.
JFYI
Dan O. - Appliance411.com http://ng.Appliance411.com/?ref411=microwave+oven
=~~~~~~
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I think you should be more respectful when shooting off your mouth (fingers) on the keyboard. You have no idea of the qualifications or background of the person you are commenting to. Maybe it can be someone who is a specialist, and has worked in the design of these things!
I think you should have respect for others. You should have asked about why you can put a metal rack in some microwave ovens, and not put someone down because of your pure ignorance!
The only reason I am answering this, is because there are many others who have some respect, and would be interested in the answer.
If you were educated in the field of physics, mechanics, or electronics, you would realize that there is something called resonance. Microwave ovens work in a particular frequency band, and therefore metal objects can be designed to not react to the frequency used in the oven. The metal cavity that the oven is constructed with, is invisible to the RF (Radio Frequency) energy being emitted from the magnetron. This metal cavity is actually a non terminated waveguide, and thus anything that is out of the exact resonance will become a load to it, and be heated up. The metal rack is designed in size and in the way it is formed to act as a near zero load to the wavelength (frequency) used. Even the paint used inside of the microwave oven must have specific characteristics. Because the cavity of the microwave oven is non terminated, is reason why the magnetron can be easily damaged if the oven is used without cooking something inside. Even the location and type of lamp used for the illumination in the microwave oven is critical.
The standard frequency used in the home cooking microwave oven is 2.45 gHz. This frequency was not pulled from rolling dice. There are a number of reasons for this choice.
Radio waves in this frequency range have a particular property where they are absorbed by water, sugars, and fats. When they are absorbed they are converted directly into heat by inducing accelerated vibration of the molecules. Microwaves in this frequency range have another interesting property. They are not absorbed by most plastics, glass, or ceramics.
Only the molecules that are being excited are heated up. This way non reacting containers will not heat up. The container of the food being cooked will only heat up by conduction from the heated food inside.
Metal reflects microwaves, which is why metal pans do not work well in a microwave oven, and can even cause damage to the magnetron by overloading it. Under some conditions, metal can conduct the microwaves and act as an induced conductor, thus converting the energy back to electricity. This is the reason why some metal object will cause sparks, and even make things catch on fire. The only exception to this is if the metal object can be in resonance to the wavelength to not be seen as a load.
There are industrial microwave type ovens that are working at other frequencies. These are used for drying specialized epoxies, curing plastics, and many other applications. There are also microwave dryers used in some types of fabric manufacturing processes. Some of these are working down at 1.5 gHz, and others are working up to about 3.5 gHz, depending on the application. These will not be good for cooking foods.
If you have one of these 2.4 gHz telephones it is normal that when you go near to your microwave oven while it is working, the phone may be interfered with. This not dangerous. There is a slight amount of energy leakage from all microwave ovens. There are specifications for this leakage. It must not exceed a particular amount.
The limit in most countries is 5 milliwatts of microwave radiation per square centimetre at approximately 2 inches from the oven surface. This is far below the level known to harm people. As you move away from an oven, the level of any leaking microwave radiation that might be reaching you decreases dramatically. For example, someone standing 20 inches from an oven would receive approximately one one-hundredth of the amount of microwaves re ceived at 2 inches. The energy drop-off works according to the inverse-square-law factor. Go to http://www.fda.gov/cdrh/consumer/microwave.html for more details about microwave oven safety and applications.
We recommend that children and pregnant women should walk away from the microwave oven while it is working. We recommend about 6 to 10 feet. This will dramatically reduce any risk of radiation absorption. There have been many studies about low level radiation from microwave ovens, TV sets, monitors, and other home appliances. There have not been anything conclusive as of yet, so it is better to not take any chances. It is known that over certain intensities, electromagnetic and RF radiation is dangerous, and will cause cancer, and other types of biological damage. The dangerous intensity level will be different at different frequencies. This is a complex field in itself. Caution is the best advice. Harmful radiation is not able to be felt, unless it is very intense. The effect of this radiation can be accumulative if the exposer is frequent.
If you want to be very safe, you should have your microwave oven checked at least once a year. The door seal and hinges can wear out. This is the greatest weakness in microwave ovens. It only takes a few thousandths of an inch of extra space to allow higher radiation leakage. The service centres that service microwave ovens should have the proper instrument to measure the microwave radiation. Some places will not charge to take the measurement. Others may charge a few dollars for the technician's time. If there is leakage, this can usually be easily repaired. Sometimes it is just the hinge adjustments, or replacing some simple parts.
We do not recommend that the consumer attempt to service his own microwave oven. It is the most dangerous appliance in the home if it is not used properly, or is opened up. The TV set and computer monitor is the second runner up to this.
--

Jerry G.
=====


"Oscar_Lives" < snipped-for-privacy@nospam.net> wrote in message
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
040604 2015 - Jerry G. posted:

I cook potatos and fish in my microwave quite often without puncturing the potato. The trick is to not cook the potato all at one time. I put a whole potato in a plastic freezer bag and fold over one time so that steam pressure can get out. I turn on the microwave on high for 1.5 minutes, then let the microwave stay off for about 2 minutes, then turn it back on for 1 minute at a time with 2 minutes off. Depending on the size of the potato, I can do 2 or 3 one minute segments, then take the potato out and place it on a rack while it is still cooking itself on the inside from its own heat. After about 2 or 3 minutes, it is ready to remove from the plastic bag and put on the plate to eat. I cook the potato with the skins on it, and place it on a paper plate. After the first cooking segment, the plastic bag puffs up and acts like an oven, steam cooking the potato. If I want fish with the potato, I put a thawed out filet of Orange Roughy in a separate plastic bag and cook it along with the potato after the first cooking segment with the potato. I sprinkle some garlic powder and Basil on the filet. This is a fast and easy way to cook a good meal. Tasty too...
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

The information about the door seal seems out of date by a couple of decades because all consumer microwave ovens made since about 1980 use choke or capacitive seals that don't rely on a tight fit, unlike the old metal fin or metal braid seals used on early microwave ovens. In fact Amana used to demonstate this in one of their commercials by slamming the face of the door with a shot put suspended from a rope and by swinging an axe into the perimeter of the door opening. Then they'd measure the leakage and show that the oven still met federal safety standards. Of course if an oven has been struck like that or dropped, it should be thrown out because you can never be sure, and it's possible that some other part of it has broken open.
Nobody should rely upon inexpensive devices to measure microwave leakage because a very high percentage of them have been shown to either not work at all (sometimes even while sitting inside a running oven) or indicate gross leakage when there is none. This is because cheap leakage detectors are built badly or aren't tuned to just the 2450 MHz oven frequency but pick up all signals, even from 60 Hz household current. The most reliable detectors may be those that use fluorescent light tubes or neon lamps, but they require a dimly lit room and won't light up unless the leakage is a few times over federal limits. Liquid crystal detectors may be better, but they can wear out in storage on the store shelf.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Newby wrote:

I agree with Jerry, but I will add that while it was foolish to do it to start with, she did the exact correct thing when she discovered her error.
--
Joseph E. Meehan

26 + 6 = 1 It's Irish Math
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

to
I hadn't made popcorn in my 1200 watt microwave for some time. So, I thought it was supposed to go for 2:50 cooking time instead of 1:50. I hit the start button. In a couple of minutes, I smelt the worst smell just as the two smoke detectors went off. Smoke was pouring from the microwave. I opened the door, and the soft "whump" sound of the bag igniting with the infusion of air made me understand in that instant I had just done the wrong thing. Now, I had lots of flames to go with lots of smoke. Ceiling to chest high thick white smoke. I opened the back door, grabbed a couple of oven mitts, and scooped out the round glass platter WITH flaming bag on top of it. Out the door we went. The dog was on the back patio doing a left right left dance, trying to anticipate which way I was going. He had the sense to cut out through the doggie door at the first sign of smoke, and probably left even before the smoke detectors went off.
I had to open up the front door, and all the windows. The smoke poured out, then lessened. I pulled the batteries from the smoke detectors that were now playing nyahh nyahh nannie at my screwup. It smelled pretty good in the house for a couple of days.
I never knew that popcorn would burn, but I guarantee you, it will. Especially when you get it really REALLY hot, and add air.
Steve
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
If you look on the front of your microwave oven, there should be a popcorn mode. There should also be a selection for the amount by weight, or volume. Use this feature. The microwave oven is designed to follow the proper cooking intensity and time combination when used in this mode. If you know the exact time, and power instensity to use, then you can do this manualy.
Popcorn is something that can be highly flamible. There is oil mixed in, and the corn is dried after it is popped. The oil is very reactive with the microwave radiation. Oil is composed of hydrodgen, and some specific types of protiens that are very reactive at the frequency of the microwave oven's radiation.
--

Jerry G.
=====


"SteveB" < snipped-for-privacy@cox.net> wrote in message
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

volume.
and
oven's
<my original anecdotal experience snipped>
Thank you so much for the oversupply of information. I was merely relating my experience with a microwave fire. I do know there is a popcorn setting on microwave ovens, having operated them since 1974. It is just that the microwave setting on my particular oven did not do just the perfect job on my popcorn. Hence, I arrived at the 1:50 time. In a moment of brain flatulence, or hitting the 2 instead of the 1, I messed up.
I thank you for correcting me, pointing out the proper use of the microwave oven, physics, and particularly thank you for the e mail pointing out this very very important matter to me.
However, my knowledge of microwaves is this: it works or it doesn't. I don't really want to or need to understand all about it, as I have other things to do, like fix the door hinges or unstop the toilet. Again. And when I put something new in my brain, something old gets kicked out to make room. So, I want to keep the 1:50 time for popcorn in there.
But thanks again for the correction and lecture. And thanks again for the personal attention of a personal e mail.
Steve
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 6/5/04 6:40 AM, Jerry G. wrote:

Not all microwave ovens I've seen have a popcorn mode. Though I think most of the new ones do.
> There should also be a selection for the amount by weight, or volume. > Use this feature. The microwave oven is designed to follow the proper > cooking intensity and time combination when used in this mode. If you > know > the exact time, and power instensity to use, then you can do this > manualy.
That makes sense, but what I don't understand is that virtually all the microwavable popcorn packages I've seen say *not* to use this feature. What's the point of a popcorn button on the microwave if the popcorn manufacturers tell you not to use it?
--
Travis
[Remove all three q's to demunge my email address.]
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
If you use the popcorn button and set the proper weight, it should work. The weight should be written on the popcorn package. The oven should then do the proper job. My family does it all the time this way.
--

Jerry G.
=====


"Travis Evans" < snipped-for-privacy@earthlinkq.netq> wrote in message
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.