This bill proposes to amend title 5 of the United States Code to expand the definition of "employees in fire protection activities." Specifically, it would include Certified Fire Investigators and members of the National Response Team within the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) under this designation. The primary purpose of this reclassification is to enable these ATF employees to receive compensation for certain illnesses and diseases that are presumed to be proximately caused by their employment in fire protection activities. This ensures they are covered under existing provisions for job-related health issues, with the amendments applying to all compensation claims filed on or after the date of the bill's enactment.