For a highly sensitive Long wave IR sensor...... like the latest upgrade to the Apaches, can see temperature variations to less that a tenth of a degree C. You can minimize the signature, but you CANNOT hide it. Remember though it is a differential signal...... the differnce between your surroundings and the temperature you emit. Obviously if the ground around you is @ 98.6 then you would be in luck if you were sitting still and not exerting yourself. Even If you are covered by a thermal shield the heat has to go somewhere. Now they may not see a human form, but they will definately see a signature of some sort.

The OP was referring to using short wave IR emitters to blind near IR sensitive cameras, or at least overload and saturate the sensor so only a white blob appears.