27 CFR § 555.220 - Table of separation distances of ammonium nitrate and blasting agents from explosives or blasting agents.

§ 555.220 Table of separation distances of ammonium nitrate and blasting agents from explosives or blasting agents.
Donor weight (pounds) Minimum separation distance of acceptor from donor when barricaded (ft.) Minimum thickness of artificial barricades (in.)
Over Not over Ammonium nitrate Blasting agent
100 3 11 12
100 300 4 14 12
300 600 5 18 12
600 1,000 6 22 12
1,000 1,600 7 25 12
1,600 2,000 8 29 12
2,000 3,000 9 32 15
3,000 4,000 10 36 15
4,000 6,000 11 40 15
6,000 8,000 12 43 20
8,000 10,000 13 47 20
10,000 12,000 14 50 20
12,000 16,000 15 54 25
16,000 20,000 16 58 25
20,000 25,000 18 65 25
25,000 30,000 19 68 30
30,000 35,000 20 72 30
35,000 40,000 21 76 30
40,000 45,000 22 79 35
45,000 50,000 23 83 35
50,000 55,000 24 86 35
55,000 60,000 25 90 35
60,000 70,000 26 94 40
70,000 80,000 28 101 40
80,000 90,000 30 108 40
90,000 100,000 32 115 40
100,000 120,000 34 122 50
120,000 140,000 37 133 50
140,000 160,000 40 144 50
160,000 180,000 44 158 50
180,000 200,000 48 173 50
200,000 220,000 52 187 60
220,000 250,000 56 202 60
250,000 275,000 60 216 60
275,000 300,000 64 230 60
Table: National Fire Protection Association (NFPA) Official Standard No. 492, 1968
Notes of Table of Separation Distances of Ammonium Nitrate and Blasting Agents From Explosives or Blasting Agents

(1) This table specifies separation distances to prevent explosion of ammonium nitrate and ammonium nitrate-based blasting agents by propagation from nearby stores of high explosives or blasting agents referred to in the table as the “donor.” Ammonium nitrate, by itself, is not considered to be a donor when applying this table. Ammonium nitrate, ammonium nitrate-fuel oil or combinations thereof are acceptors. If stores of ammonium nitrate are located within the sympathetic detonation distance of explosives or blasting agents, one-half the mass of the ammonium nitrate is to be included in the mass of the donor.

(2) When the ammonium nitrate and/or blasting agent is not barricaded, the distances shown in the table must be multiplied by six. These distances allow for the possibility of high velocity metal fragments from mixers, hoppers, truck bodies, sheet metal structures, metal containers, and the like which may enclose the “donor.” Where explosives storage is in bullet-resistant magazines or where the storage is protected by a bullet-resistant wall, distances and barricade thicknesses in excess of those prescribed in the table in § 555.218 are not required.

(3) These distances apply to all ammonium nitrate with respect to its separation from stores of high explosives and blasting agents. Ammonium nitrate explosive mixtures that are high explosives pursuant to § 555.202(a) or are defined as a blasting agent pursuant to § 555.11 are subject to the table of distances for storage of explosive materials in § 555.218 and to the table of separation distances of ammonium nitrate and blasting agents from explosives or blasting agents in this section.

(4) These distances apply to blasting agents which pass the insensitivity test prescribed in regulations of the U.S. Department of Transportation (49 CFR part 173).

(5) Earth or sand dikes, or enclosures filled with the prescribed minimum thickness of earth or sand are acceptable artificial barricades. Natural barricades, such as hills or timber of sufficient density that the surrounding exposures which require protection cannot be seen from the “donor” when the trees are bare of leaves, are also acceptable.

(6) For determining the distances to be maintained from inhabited buildings, passenger railways, and public highways, use the table in § 555.218.

[T.D. ATF-87, 46 FR 40384, Aug. 7, 1981, as amended by ATF 2017R-21, 84 FR 13800, Apr. 8, 2019; ATF 2002R-226F, 84 FR 12097, Apr. 1, 2019]