Preliminary Findings of the U.S. Chemical Safety Board 

from its Investigation of the West Fertilizer Explosion and Fire 

The CSB has made the following observations and preliminary findings to date, which are 

subject to further revision and development as the investigation unfolds: 

1) The explosion at West Fertilizer resulted from an intense fire in a wooden warehouse 

building that led to the detonation of approximately 30 tons of AN stored inside in 

wooden bins. Not only were the warehouse and bins combustible, but the building also 

contained significant amounts of combustible seeds, which likely contributed to the 

intensity of the fire. According to available seismic data, the explosion was a very 

powerful event. 

2) Whether additional factors such as material characteristics, shock, or contamination 

contributed to the incident remains to be determined. Company employees described a 

PVC plastic pipe that was located directly above the AN bin that detonated, and likely 

would have been melted by the fire. Additionally, large amounts of potentially 

flammable anhydrous ammonia were stored along the southern edge of the warehouse 

building. 

3) The building lacked a sprinkler system or other systems to automatically detect or 

suppress fire, especially when the building was unoccupied after hours. By the time 

firefighters were able to reach the site, the fire was intense and out of control. Just 20 

minutes after the first notification to the West Volunteer Fire Department, the 

detonation occurred. 

4) Both National Fire Protection Association (NFPA) and the International Code Council 

(ICC), private organizations that develop fire codes that are widely applied across the 

U.S., have written code provisions for the safety of ammonium nitrate. Many of these 

safety provisions are quite old1

 and appear to be confusing or contradictory, even to 

code experts, and are in need of a comprehensive review in light of the West disaster 

and other recent accidents. For example the ICC’s International Fire Code directs users 

to a defunct code for ammonium nitrate (NFPA 490, last issued in 2002) rather than the 

current code, known as NFPA 400. 

5) The existing fire codes do contain some useful provisions; for example the codes do 

require a fire resistant barrier between AN and any stored flammable or combustible 

materials and have provisions to avoid AN confinement and promote ventilation during 

fire conditions. However, even the most current NFPA 400 standard allows AN to be 

stored in wooden buildings and in wooden bins, and does not mandate automatic 

sprinkler systems unless more than 2500 tons of AN is being stored – vastly more than 

the approximately 30 tons that was sufficient to devastate much of the town of West. 

In addition, the standard contains a “grandfathering” provision that allows existing 

buildings that were constructed prior to code adoption – and fail to meet all of its 

provisions – to continue in use. 

                                                           

1

 NFPA 400 refers users to a 1953 publication by the U.S. Bureau of Mines for information on the explosive 

properties of AN. 
6) Texas has not adopted a statewide fire code, and state law actually prohibits most 

smaller rural counties from adopting a fire code. McLennan County, where the West 

facility was located, had not adopted a fire code, although it technically had the 

authority to do so because of its proximity to the more populous Bell County. The 

West Fertilizer facility was thus not required to follow any NFPA or ICC 

recommendations for the storage of AN. 

7) Although some U.S. distributors have constructed fire-resistant concrete structures for 

storing AN, fertilizer industry officials have reported to the CSB that wooden buildings 

are still the norm for the distribution of AN fertilizer across the U.S. 

8) Industry has developed other forms of ammonium nitrate that are reported to reduce or 

eliminate the risk of accidental detonation. For example, compounding the ammonium 

nitrate with calcium carbonate (limestone) “practically eliminates any risk of explosion 

in its storage, transportation, and handling,” while preserving the AN’s nutritive value.2

 

Calcium ammonium nitrate fertilizers have been widely used in Europe. Ammonium 

sulfate nitrate also has been found to be non-explosive provided the percentage of AN 

is held below about 37%.3

9) The federal OSHA standard for “Explosives and Blasting Agents” (29 CFR 1910.109) 

does have requirements for ammonium nitrate fertilizer; its provisions are similar to the 

NFPA codes. Unlike the NFPA codes – which West was not legally required to follow 

under any fire code – the OSHA standard would have applied. Like NFPA, however, 

the OSHA standard does not prohibit wooden bins or wooden construction, and does 

not require sprinklers unless more than 2500 tons of AN is present. However, OSHA 

public records indicate that OSHA last inspected the facility in 1985, and no citations 

were issued under the “Explosives and Blasting Agents” standard. 

10) OSHA’s Process Safety Management standard (29 CFR 1910.119) or PSM was 

adopted in 1992 and is designed to prevent catastrophic workplace incidents involving 

highly hazardous chemicals. PSM requires companies to have a variety of management 

elements to prevent catastrophic incidents, such as conducting hazard analyses and 

developing emergency plans. Ammonium nitrate is not, however, one of the listed 

chemicals that triggers PSM coverage. The PSM standard also contains an exemption 

for retail facilities. 

11) The EPA’s Risk Management Program rule (40 CFR Part 68) or RMP was adopted in 

1996 and is designed to prevent catastrophic offsite and environmental damage from 

extremely hazardous substances. As the name suggests, the rule requires covered 

facilities to develop a Risk Management Plan, implement various safety programs, and 

analyze offsite consequences from potential accidents. Once again, however, 

ammonium nitrate is not one of the listed chemicals that triggers RMP coverage. West 

Fertilizer was RMP-covered due to its stored ammonia, and the company’s offsite 

consequence analysis considered only the possibility of an ammonia leak, not an 

explosion of ammonium nitrate. 

                                                           

2

 Calcium ammonium nitrate (CAN) must still be protected from contamination with other chemicals that can resensitize it to detonation. See Popovici Ipochim, N.N.; Icechim, M.M.; “Other Ammonium Nitrate Fertilizers;” In 

Keleti, C. (ed.); Nitric Acid and Fertilizer Nitrates; New York: Marcel Dekker Inc., 1985. 3 Ibid.
12) OSHA considered adding ammonium nitrate along with other highly reactive chemicals 

to its list of PSM-covered substances in the late 1990’s. However, this proposal was 

shelved in 2001. In developing the RMP regulation, the EPA did not explicitly include 

explosives or reactive chemicals in the list of covered chemicals. In 2002, the CSB 

issued a study on reactive hazards, identifying 167 prior reactive incidents (including a 

1994 explosion at an ammonium nitrate manufacturer). The Board recommended that 

both OSHA and EPA expand their standards to include reactive chemicals and hazards. 

However, neither agency has yet acted upon the recommendations. 

13) No federal, state, or local standards have been identified that restrict the siting of 

ammonium nitrate storage facilities in the vicinity of homes, schools, businesses, and 

health care facilities. In West, Texas, there were hundreds of such buildings within a 

mile radius, which were exposed to serious or life-threatening hazards when the 

explosion occurred on April 17. 

14) West volunteer firefighters were not made aware of the explosion hazard from the AN 

stored at West Fertilizer, and were caught in harm’s way when the blast occurred. 

NFPA recommends that firefighters evacuate from AN fires of “massive and 

uncontrollable proportions.” Federal DOT guidance contained in the Emergency 

Response Guidebook, which is widely used by firefighters, suggests fighting even large 

ammonium nitrate fertilizer fires by “flood[ing] the area with water from a distance.” 

However, the response guidance appears to be vague since terms such as “massive,” 

“uncontrollable,” “large,” and “distance” are not clearly defined. All of these 

provisions should be reviewed and harmonized in light of the West disaster to ensure 

that firefighters are adequately protected and are not put into danger protecting property 

alone. 

15) While U.S. standards for ammonium nitrate have apparently remained static for 

decades, other countries have more rigorous standards covering both storage and siting 

of nearby buildings. For example, the U.K.’s Health and Safety Executive states in 

guidance dating to 1996 that “ammonium nitrate should normally be stored in single 

storey, dedicated, well-ventilated buildings that are constructed from materials that will 

not burn, such as concrete, bricks or steel.”4 The U.K. guidance calls for storage bays 

“constructed of a material that does not burn, preferably concrete.” 

16) CF Industries, a principal manufacturer of AN that was one of the suppliers to West, 

also recommends more rigorous safeguards in its Material Safety Data Sheet (MSDS) 

for the chemical. In the section entitled “Handling and Storage,” CF recommends that 

“Storage construction should be of non-combustible materials and preferably equipped 

with an automatic sprinkler system.”5

 Although companies are required to issue 

MSDS’s, the recipients of this information like West Fertilizer are not obligated to 

follow the recommended safety precautions. West lacked these safeguards. 

17) The Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) has regulations for 

ammonium nitrate used as an explosive but these do not apply to ammonium nitrate 

used as fertilizer. The U.S. Department of Homeland Security has reporting 

                                                           

4

 U.K. Health and Safety Executive; “Storing and Handling Ammonium Nitrate;” Available from 

http://www.hse.gov.uk/pubns/indg230.pdf 

5 http://www.cfindustries.com/pdf/Ammonium-Nitrate-Amtrate-MSDS.pdf
requirements for companies that have a threshold amount of fertilizer grade ammonium 

nitrate. However, the authority of DHS is to require security measures to protect 

against theft, diversion, or other intentional acts; DHS does not regulate the safety of 

ammonium nitrate to prevent conditions leading to accidental detonation. 

18) The Emergency Planning and Community Right-to-Know Act of 1986 (EPCRA) 

contains an exemption from hazardous chemical reporting for “fertilizer held for sale 

by a retailer to the ultimate customer.” The EPA has interpreted this provision as not 

applying to firms, like West, that make custom blends of bulk fertilizer for customers’ 

use. In 2012, West Fertilizer filed an EPCRA Tier II report with the McLennan County 

Local Emergency Planning Committee (LEPC). West reported the presence of up to 

270 tons of ammonium nitrate, as well as anhydrous ammonia, at the site. The 

company did not provide the LEPC or the West Fire Department with an ammonium 

nitrate MSDS indicating the material’s hazards, nor does EPCRA automatically require 

that information to be provided. There is no indication that West’s filing with local 

authorities resulted in an effort to plan for an ammonium nitrate emergency.