This guy says covering yourself with a $3 space blanket will work. But I’m skeptical. Wouldn’t a an IR camera be able to detect someone wrapped in a space blanket if they’ve been wrapped in it for a while? I’m thinking this might occur because the blanket would eventually warm up due to the person’s body heat, and thus emit some IR.
Seems reasonable enough. I wonder what the pictures would look like if the ambiant air temp was between 98 and 99 degrees F?
Even at the same temperature, bare aluminum emits much less IR than, say, human skin. Or most non-metallic surfaces, for that matter. So I’m not surprised to hear it remained effective after 30 minutes.
But that’s bare, clean aluminum. Heavily oxidized aluminum will be less effective. Aluminized mylar with the mylar side facing out is even worse, because the mylar emits a lot of IR. I’m guessing the “survival blanket” had transparent plastic on top of the metallic coating - otherwise I’m hard pressed to explain the dramatic difference between the “survival blanket” and “space blanket”.
As long as you’re hotter than your environment, whatever you cover yourself in is eventually going to warm up to your temperature and start emitting more IR than the background. Even if the emissivity is low, it’s still going to increase – all that heat has to go somewhere.
The ideal thing would be to have a refrigerated suit that stayed the same tem,perature as the outside world, with the heat exchanger away from the IR camera or otherwise out of sight. Either that, or surround yourself with something having enough thermal mass so that you won’t heat it up fast. But I suspect it’d be too heavy and clumsy to use.
Whatever you do, don’t put yourself against a colder background, as the heroine in Hardware did – that’s like hiding a lit candle in a dark room. (Bad movie). I don’t think coating yourself with mud, a la Arnold in Predator, will do any good, either.
Of science fiction movies, the only one that got it right (that I know of) is Tremors II – cool your clothes down so they’re cold, and mask your body heat. As long as your antagonist either can’t sense “holes” in the background, or doesn’t care about them, you’re OK.
The other alternative is to heat up the background so you’ll blend in. That’s usually impractical. (They supposedly did this in the movie Sneakers, but that’s one ridiculous heating system that could heat up whole room to 98.6 degrees. (and without giving off any warning alarms, yet.)
Well, it wouldn’t work for running around in. But if you crawl up onto a muddy bank, roll in the cool mud, and then lay still, wouldn’t that work, as least for a few minutes?
Yes, but emissivity of polished aluminum is around 0.02, meaning it emits only 2% as much IR as a perfect blackbody. Assuming body temperature of 36.0[sup]o[/sup]C and room temperature of 20.0[sup]o[/sup]C, wrapping yourself in clean polished aluminum will make you look like you’re only 20.35[sup]o[/sup]C. Not perfectly invisible, but it’s still a pretty effective way to minimize your visibility.
This calculation assumes your aluminum covering is mostly reflecting emission from the 20[sup]o[/sup]C room. If you’re outside and standing against a solid background, an aluminum covering can make you look cooler than the background, because the aluminum will mostly reflect the sky which is much colder than your background. That seems to be what’s happening in the OP’s link; the guy wearing the space blanket looks darker than the surroundings.
Radiation is not the only way to get rid of heat. I don’t think exhaled breath is visible on a typical IR camera, for example.
And now I’m going to be a killjoy and (rather obviously) point out that being invisible to IR is pretty darned useless if you’re otherwise visible. 
I’ve always imagined wrapping yourself in ice packs.
Good news: Yes, this will work quite well.
Bad news: It will only work with the equipment Predators have. For other situations, your shit is gonna be in the wind. 
Infared Camera’s are blinded by Bright direct Light. When recording at night, the bright Mercury-vapor lights (and alike) blind the camera in a starburst effect. By shining a million-candled flashlight at an infared camera, you will not be seen.
I actually tried the blanket techinique once (a regular blanket) with some friends. They didn’t believe it would work, but I knew they were good heat insulators. We went in front of some infrared alarm sensors and lo’ and behold, they didn’t go off. Then one of those dummies said, “I don’t think the alarms are on,” and removed his blanket, setting off the alarm. That’s pretty good proof to me. We weren’t under the blankets long enough (only a few minutes) to assess their long-term viability though. I may have to try that some time.
You could try standing in a burning building.
That’s almost as snide as the thought that occurred to me: Lower your body temperature to the ambient temperature. (Of course, you’ll be hypothermic at that point, unless you’re in a 90-degree-plus environment.
How about, hide in a steam room?
Unfortunately, this won’t work. Depending primarily upon humidity, the emissivity of air is pretty close to zero. It will increase with humidity somewhat, but it will always be much lower than human skin or clothing. The air around you would have to be significantly warmer than you in order to mask your IR signature. Even on a 100-degree day, your heat signature sticks out like a sore thumb on an IR image.
At a place where I used to work, the alarm installation guy reassured us that the cameras we had (which had motion and IR and other stuff) wouldn’t pick up stuff outside the shop. Otherwise they’d be picking up traffic, and people standing outside the window, and stuff like that.
So walk around in a massive glass box and you’ll be fine.
Get dead; really, really dead.
This really depends on what kind of IR device you’re talking about. If you’re talking about a thermographic camera that picks up all the emissivity, there’s not much you can do short of encasing yourself in a thermos. If you’re talking about a near-IR device that only picks up IR reflectivity, such as night-vision goggles, you might be interested in what I found in this thread on camouflage
I think by “ambient temperature” he meant the temperature of the surrounding walls and floor. This should work.
As others have said, assume the same temperature as your surroundings. The details are left as an exercise for the student.
I would say that wouldn’t work - all of the models of thermal imaging cameras I’ve used have seen people inside burning buildings.
My answer is to bring the background temperature up. That has stopped our cameras from working “normally” on hot summer days. You can still see the temperature differential across someone’s body, though. Top of their head, armpits, and anything not covered in clothing will still show up whiter than the rest of the person. You’d need to get the person to be the same temperature all the way around as well as bring the background temperature up.