Patent Number: 
Section: claims

1. An infrared marking device comprising:a ring-shaped, elasticized outer sleeve having a tubular sidewall; andan amount of a self-heating material confined inside said tubular sidewall of said outer sleeve, said self-heating material emitting infrared radiation when activated to initiate an exothermic chemical reaction. 2. The infrared marking device of claim 1 wherein said sidewall of said outer sleeve is permeable to oxygen, and said self-heating material reacts exothermally when exposed to the oxygen permeating through said sidewall. 3. The infrared marking device of claim 1 further comprising:a ring-shaped elastic band positioned inside said outer sleeve and extending circumferentially about said outer sleeve, said elastic band operating to elasticize said outer sleeve. 4. The infrared marking device of claim 3 wherein said tubular sidewall comprises a first lumen confining said elastic band and a second lumen confining said self-heating material. 5. The infrared marking device of claim 1 further comprising:an enclosure holding said outer sleeve, said enclosure being formed from a material that prevents oxygen from reaching said self-heating material inside said outer sleeve. 6. The infrared marking device of claim 5 further comprising:a plurality of air permeable pouches disposed inside said outer sleeve, wherein said amount of said self-heating material is distributed among said air permeable pouches and confined inside said air permeable pouches. 7. The infrared marking device of claim 6 wherein said sidewall of said outer sleeve is divided into a plurality of compartments each containing at least one of the air permeable pouches. 8. The infrared marking device of claim 1 wherein said self-heating material comprises a loose powder distributed inside said outer sleeve. 9. The infrared marking device of claim 8 wherein said sidewall of said outer sleeve is divided into a plurality of compartments, and said loose powder is distributed among said compartments. 10. The infrared marking device of claim 1 wherein said outer sleeve has a relaxed circumference of about 12 inches and a stretched circumference ranging from about 24 inches to about 36 inches. 11. The infrared marking device of claim 1 wherein said self-heating material exothermally heats to a temperature between approximately 135° F. to approximately 175° F. 12. The infrared marking device of claim 1 wherein said self-heating material exothermally heats to a temperature imageable in a thermal imaging camera. 13. A method for marking a door inside a structure, the method comprising:activating a self-heating material confined inside a marking device to initiate an exothermic reaction that emits infrared radiation;coupling a first portion of the marking device with a first door knob of the door. 14. The method of claim 13 further comprising:coupling a second portion of the marking device with a second door knob so that the marking device extends between the first and second door knobs. 15. The method of claim 13 wherein activating the self-heating material further comprises:exposing the self-heating material to oxygen to initiate the exothermic reaction that activates the self-heating material. 16. A method for marking an object inside a structure, the method comprising:activating a self-heating material confined inside the marking device to initiate an exothermic reaction that emits infrared radiation;wrapping a marking device about a gloved hand or a handle of an axe; andcarrying the marking device into the structure. 17. The method of claim 16 wherein the object is a door, and applying the marking device further comprises:moving the gloved hand relative to a first door knob to couple a first portion of the marking device with the first door knob; andmoving the gloved hand relative to a second door knob to couple a second portion of the marking device with the second door knob so that the marking device extends between the first and second door knobs. 18. The method of claim 13 further comprising:entering the door to search a room inside the structure before the marking device is applied to the door. 19. The method of claim 13 further comprising:imaging a heat signature of the marking device in a thermal imaging camera. 20. The method of claim 16 further comprising:applying the marking device to the object inside the structure.