Burn bag

A burn bag is a security bag that holds sensitive or classified documents which are to be destroyed by fire or pulping after a certain period of time. The most common usage of burn bags is by government institutions, in the destruction of classified materials.
Burn bags are designed to facilitate the destruction process by not requiring the removal of the items to be destroyed beforehand and by indicating if the items require special procedures. Destruction via burn bags is considered superior to shredding, because shredded documents may be reconstructed. After the capture of the United States embassy in Tehran during the Iran hostage crisis, shredded documents were turned over for painstaking manual reconstruction, which revealed to Iran some U.S. operations including spies. 
Usage.
In government institutions.
Burn bags are generally associated with US governmental organizations like the CIA and NSA, due to the classified nature of their work. Most other governmental organizations have some form of burn bag system to destroy documents deemed of a Top Secret, Secret, Classified, or other similar nature. 
Burn bags are mostly used to satisfy destruction of articles pursuant under Executive Order 12958 section 1.4, in part: 
Classified information must fall under one of the following categories:<br>
1.4 (a) Military plans, weapons systems, or operations;<br>
1.4 (b) Foreign government information;<br>
1.4 (c) Intelligence activities, sources or methods or cryptology;<br>
1.4 (d) Foreign relations or foreign activities of the United States including<br>
1.4 (e) Scientific, technological or economic matters relating to national security;<br>
1.4 (f) United States Government programs for safeguarding nuclear materials or facilities;<br>
1.4 (g) Vulnerabilities or capabilities of systems, installations, projects or plan relating to the national security; or,<br>
1.4 (h) weapons of mass destruction
The order was subsequently replaced by Executive Order 13526.
Due to environmental concerns and the high value of recycled paper, institutions that generate large amounts of classified material tend to securely desensitize their data in disintegrators with a 3/32" NSA/DOD approved top-secret screen. Even though the moniker "Burn Bag" is still very popular, rarely within the United States is classified material incinerated.
Overseas military outposts and diplomatic missions frequently have emergency disposal procedures in place for the rapid burning of classified materials. These often include special burn bags with built-in thermite charges.
Haz-mat usage.
The term "burn bag" can also refer to bags that contain haz-mat protective gear after inspection of sources deemed hazardous.
In private businesses.
Document Destruction Companies have rarely used burning in disposing of documents, mainly opting to shred material before disposal. However, due to the possibility that shredded material can be reconstructed, and recent increases in identity theft and corporate espionage, some services have started to offer destruction by burning instead of disposal into landfills.
The waste-to-energy industry often offers a "secure disposal" service to allow businesses to use the waste-to-energy plants' municipal waste incineration units for sensitive material disposal. Services range from a basic drop-off at the facility to actually having a witness to the incineration process and issuance of a certificate of destruction.