In the wake of the Oklahoma City bombing in 1995, the government classified all buildings into five security levels and established minimum security requirements for them.[1]
Level V
These buildings contain mission functions critical to national security, such as the Pentagon, CIA Headquarters, and ARTCCs. A Level-V building should be similar to a Level-IV building in terms of number of employees and square footage. It should have at least the security features of a Level-IV building. The missions of Level-V buildings require that tenant agencies secure the site according to their own requirements.
Level IV
This type of building has 450 or more federal employees; high volume of public contact; more than 150,000 square feet (14,000 m2) of space; and tenant agencies that may include high-risk law enforcement and intelligence agencies (e.g., ATF, FBI, and DEA), the Federal courts, and judicial offices, and highly sensitive government records.
Level III
This is a building with 151 to 450 federal employees; moderate/high volume of public contact; 80,000 to 150,000 square feet (14,000 m2) of space; and tenant agencies that may include law enforcement agencies, court/related agencies and functions, and government records and archives. (According to GSA, at the request of the Judiciary, GSA changed the designation of a number of buildings housing agencies with court and court-related functions from Level III to Level IV.)
Level II
This type of building has 11 to 150 federal employees; moderate volume of public contact; 2,500 to 80,000 square feet (7,400 m2) of space; and federal activities that are routine in nature, similar to commercial activities.
Level I
This type of building has 10 or fewer federal employees; low volume of public contact or contact with only a small segment of the population; and 2,500 or less square feet of space, such as a small store front type of operation. This type of building is more vulnerable to attack.
