Would mylar strips reduce the thermal image? FLIR doesn't care how good your camo is. Would be interested in ideas about masking the heat signature.
The trick is for the amount of thermal radiation emitted from you to be about equal to the thermal radiation emitted from your surroundings (or at least some part of your surroundings, such as stones or foliage). This is related to two properties of the material you're covered with: its temperature, and its thermal emissivity. I think that if a material could be found which, at human body temperature, gave off the same amount of IR radiation as grass, dirt, or foliage, that might do the trick. But I need to read up on this some more. I don't own a thermal camera, but at some point I may rent or even buy one to do experiments. If others have this capability, I hope they will do so, too. Then we can all share what we learn. This is a problem that needs to be tackled so citizens can be safer from monitoring, at least at night.
For now, I can tell you that infrared cameras do not give x-ray vision. They can't see through walls (though they can detect someone leaning on a wall and heating it from the other side), heavy tree cover, or most other barriers. Check out some YouTube videos of suspects being chased by cops who have FLIR-equipped helicopters. You can see from those videos that the suspects' IR signatures practically disappear whenever they run under tree cover. Thus, escaping into a heavy forest would probably work even without camouflage. (Urban environments also create lots of thermal "clutter," reducing the effectiveness of FLIR.)
Even a big umbrella covering you will block your IR signature, though you'd need some way of camouflaging the umbrella (preferably by attaching plenty of still-fresh foliage to it).
Combining such countermeasures with very rainy weather would probably be even more effective. I once read a special forces guy refer to that kind of weather as "special forces weather." The greater stealth that such weather allows is clearly the reason.
