WINSTON-SALEM, N.C. (WGHP) — The North Carolina Department of Labor has opened an investigation into why and how a dangerous chemical fire broke out Jan. 31 at Weaver Fertilizer in Winston-Salem even as questions continue to emerge about how safely the company stored massive amounts of an explosive chemical compound.

Responding to a request for state inspection reports at Weaver, Rose Gray of the NCDOL’s Division of Occupational Safety and Health confirmed in an email to WGHP that a formal inquiry is underway.

“That investigation was opened 2/1/22 in relation to the fire that occurred,” Gray wrote.

WGHP had asked for inspection reports because Weaver had stored large amounts of ammonium nitrate on site, a compound that could have exploded or fueled a blaze from another source. That threat caused the area surrounding the plant at 4440 Cherry Street to be evacuated for several days as the fire burned down.

In her original response to WGHP’s request, Gray, the statistical and historical document processor in OSH, had written that the state’s inspection of Weaver for one of the records sought was “not complete at this time.”

Why was the fertilizer plant that caught fire in Winston-Salem storing 600 tons of flammable material
Why was the fertilizer plant that caught fire in Winston-Salem storing 600 tons of flammable material

“Once completed, the company will be notified of the results of the inspection by receiving applicable citations or an in-compliance letter,” the letter said. “Upon receipt of inspection results, a company or an employee also has the option of requesting an informal conference or to contest a file. During the informal conference and/or stages, no information (except citations and de minims notices, proposed penalties, and matters of public record such as pleadings before the OSH Review Commission or the court system) will be released from the case file.”

Weaver Fertilizer fire evacuation area
Weaver Fertilizer fire evacuation area

Gray then verified in a subsequent email that the investigation had been opened.

Weaver had stored about 600 tons on ammonium nitrate on property. That compound is not in and of itself combustible, although at certain levels of heat it can explode. It also is an accelerant for a blaze that begins separately.

Ammonium nitrate has contributed to significant explosions and loss of life in West Texas and Beirut, Lebanon, most recently. There was no explosion in Winston-Salem, but officials feared that threat for four days.

Investigative process

Take a look inside the incident command center set up to deal with Winston-Salem fertilizer plant fire, help evacuations
Take a look inside the incident command center set up to deal with Winston-Salem fertilizer plant fire, help evacuations

The NCDOL says on its website that an investigation is triggered by loss of life or significant injury caused by a workplace incident, which employers are required to report.

OSH investigations usually are limited to the event “unless observations at the site indicate a broader investigation is needed.”

OSH then would send an investigator to the site to determine the cause of incident, whether OSH safety or health standards were violated and what role that violation may have played in the incident. Investigators would collect physical evidence, take photographs and interview principals to determine the cause of the incident. That process can take a few weeks or perhaps months, depending on how involved the event is, and it’s unclear what NCDOL has accomplished.

If violations of workplace standards are found, citations would be issued (and shared publicly), but details of the investigation would not be public until the case is closed.

Standards for storage

Fertilizer plant fire continues to rage 12 hours on; neighbors asked to evacuate due to risk of explosion
Fire at the Weaver Fertilizer Plant in Winston-Salem, N.C. (WGHP)

Matt Barker, a senior chemical engineer for the National Fire Protection Association, which describes itself as a national nonprofit organization devoted to eliminating death, injury, property, and economic loss because of fire, electrical and related hazards. has standards that are used by many states. The NFPA describes requirements for safely storing ammonium nitrate under NFPA 400, the “Hazardous Materials Code.”

Those standards include storing ammonium nitrate away from substances “that can cause ammonium nitrate to destabilize;” in facilities located a safe distance from other structures or people; in a place that avoids contamination or confinement; and outside basements and combustible bins.

Companies are required to notify local officials about the type and quantity of the ammonium nitrate stored at the facility, to have an emergency response plan and to “have constant fire monitoring.”

Charlie Johnson, chief fire code consultant for the NC Department of Insurance’s Office of State Fire Marshal, said state fire code often relies on standards set by NFPA.

“Many of the NFPA standards are referenced for certain applications [in the fire code],” Johnson wrote in an email Tuesday. “As an example, Chapter 80 of the fire code contains a reference to NFPA 400, Hazardous Materials Code. Section 6304.1.2 requires a sprinkler system in oxidizer storage buildings to comply with NFPA 400.

“Sometimes it’s not that full standard referenced, only a given section.”

Johnson has said previously that because Weaver’s facility is so old – built in the late 1930s for an opening in 1940 – that it was not required to operate under current requirements for fire monitoring and sprinkler equipment. Only new and remodeled facilities are required to do so.

Weaver was “required to comply with the code in effect when they were originally constructed,” he said.

The NFPA’s latest edition of NFPA 400 do include retroactive requirements for existing facilities that do apply to older fertilizer buildings, such as Weaver’s “These requirements were added in response to the West, TX fire with the intent of preventing future fires and other hazardous incidents at such facilities,” NFPA Communications Manager Susan McKelvey wrote in a follow-up email. “If a jurisdiction adopts the 2016, 2019, or 2022 edition of NFPA 400 directly or by reference from another fire code, such as NFPA 1, Fire Code or the International Fire Code (IFC), then older ammonium nitrate facilities are not exempt from the modern requirements.”

Johnson said earlier that there were limits on how flammable materials could be stored.

“In general, the code allows a certain amount of flammable/combustible materials and if that amount is exceeded, the building could be classified as hazardous and require a sprinkler system or other fire protection,” he said.

CORRECTION & CLARIFICATION: This article has been updated with additional information and clarifies how the NFPA should be described. Senior Engineer Matt Barker’s name was misspelled.