ATF eRegulations

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

1. 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

2. 1. Table: National Fire Protection Association (NFPA) Official Standard No. 492, 1968

   2. Notes of Table of Separation Distances of Ammonium Nitrate and Blasting Agents From Explosives or Blasting Agents
   3. (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.

   4. (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.

   5. (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.

   6. (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).

   7. (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.

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