- American Indians
- Americans with Disabilities Act
- Ammunition
- Amplifiers
- Amputation
- Amusement Parks
- Anatomy
- Anesthesia
- ANI
- Animal Bites
- Animals
- Antennas
- Anthrax
- Anthropology
- Antishock Garments
- Antistatic Material
- Antitrust Laws
- Anxiety
- AOR
- Apartments
- Appliances
- Apprenticeship
- Appropriations
- Aptitude Tests
- Aquatic Hazards
- Aqueous Film Forming Foams
- ARAC
- Arbitration
- Archaeology
- Archeology
- Arches
- ARCHIE
- Architects
- Architecture
- Archives
- Area of Refuge
- Arenas
- ARFF Crash Fire Rescue
- Armed Forces
- Armories
- Arms Control
- Arms Race
- Arms Sales
- Army National Guard Bureau
- Arrests
- Arrhythmia
- Arsenic
- Arson
- Arson For Profit
- Arson Information Management System
- Arson Prevention
- Arson Squads
- Arson Strike Forces
- Arson Task Forces
- Arson Units
- Arsonists
- Arthritis
- Asbestos
- Ash
- Asphalt
- Asphyxiation
- Aspirators
- Assessment Centers
- Astronautics
- Astronauts
- Astronomy
- Atlases
- ATLS
- Atmosphere
- Atmospheric Release Advisory Capability
- Atomic Energy
- Atomic Energynt
- Atomic Industries
- Atomic Power Plants
- Atomic Radiation
- Atomic Reactors
- Atomic Research
- Atomic Tests
- Atomic Warfare
- Atriums
- Attack Line
- Attics
- Attitudes
- Attorneys
- Attrition
- ATV
- Audiovisual Equipment
- Audiovisual Materials
- Auditing
- Authorities Having Jurisdiction
- Autism
- Automated Construction Estimation System
- Automated Defibrillators
- Automated External Defibrillators
- Automated Resource For Chemical Hazard Incident Evaluation
- Automatic Aid
- Automatic Defibrillators
- Automatic Fire Protection Systems
- Automatic Location Identification
- Automatic Number Identification