Explosion in China Draws Attention to Combustible Metal Dust

Combustible dust accidents continue to make news worldwide, and the most recent incident occurred in Kunshan, China, about 30 miles west of Shanghai. A blast caused by aluminum and magnesium dust at Kunshan Zhongrong Metal Products Co. took place on the morning of August 2, killing 75 and injuring 185. Workers at the facility polished wheel rims for car companies like GM, and this process created excessive amounts of dust.

The factory lacked proper dust removal equipment, which caused the dust to build up throughout the facility. Workers told reporters the face masks provided to them didn’t keep the dust from getting into their noses and mouths, and by the end of a shift dust coated them.

In the weeks since the incident, China has begun investigating other factories at risk for combustible dust hazards and plans to scrutinize current safety policies for workplaces like this metal products company in Kunshan, according to Bloomberg Businessweek.

Metal Dust Explosions in Recent Years

Combustible dust explosions aren’t a new problem in China. The country has experienced a number of combustible dust explosions in recent years, and a 2011 explosion at a plant operated by Foxconn, which supplies large companies like Apple, Dell and Sony, received a significant amount of international attention. The plant polished metal parts for electronics, and when combustible dust in an air duct exploded, three workers were killed and 15 were injured.

Metal Dust, Combustible Dust
If fine enough, metal dusts can be flammable. Photo: Wikimedia Commons/W. Oelen

Metal dust isn’t just a problem abroad, though. According to the Chemical Safety Board (CSB), between 1980 and 2005, 281 combustible dust accidents occurred in the U.S. that caused 119 worker deaths.

The CSB recently released a report about a 2010 metal dust explosion at AL Solutions, a titanium and zirconium scrap metal processor in West Virginia. The report concluded the dust housekeeping measures used at the facility weren’t enough to prevent explosions from titanium and zirconium dust. As a result of the accident, three employees were killed.

An explosion in April of this year at a company called Gorilla Polishing outside of Los Angeles also demonstrates that accidents that happen abroad can easily happen here, too, if employers don’t take proper safety precautions. Workers at the facility were polishing wheel rims when an explosion occurred, likely because of an accumulation of dust in the building’s duct system. Eleven workers were injured, many of them seriously.

Many people may assume that metal dust doesn’t pose a serious fire and explosion hazard because metal isn’t flammable in solid form. In a fine particle form, however, it is quite flammable. Titanium, for example, has a flammability rating of 3 or 4 (with 4 being the highest hazard level).

Many unexpected materials pose a combustible dust hazard under the right conditions, so employers and employees need to understand what precautions to take to avoid accidents.

Combustible Dust Prevention Measures

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Five components must be present for a combustible dust explosion to occur. Image: OSHA

First, employers and safety managers should learn about the conditions that will lead to a combustible dust accident. A dust fire requires fuel (dust), oxygen and a heat source. For a fire to escalate to an explosion there must also be a significant amount of dust dispersing through the air (like a dust cloud) and the space must be confined (any walled room is considered a confined space when it comes to combustible dust).

These conditions aren’t often present in the workplace all at once, but they are common conditions, so explosions are possible.

To prevent accidents, workplaces can focus on reducing the risky conditions that are within their control like dispersing dust and heat sources. Implementing housekeeping measures like cleaning up dust from work processes on a daily basis, washing down the workplace with water and clearing dust from flat surfaces near the ceiling are important.

As seen in the case of AL Solutions, though, sometimes housekeeping measures cannot adequately control dust. The National Fire Protection Association (NFPA) advises employers to install dust collection systems so dust is immediately diverted away from the workspace.

Employers should also make sure machinery, dust collectors and ducts are all grounded so static electricity doesn’t cause a spark that could start a fire. Employees should use extra caution when performing tasks that involve heat or sparks like welding.

Special Metal Dust Precautions

combustible dust, dust fire
Metal dust fires require special fire extinguishers.

Metal dust has been the culprit in many combustible dust explosions, and workplaces and firefighters both need to prepare for these types of fires. Mainly, it is important to know how to put out a metal fire. Traditional methods for quenching fires like water and fire extinguishers can actually make the situation more dangerous if people aren’t careful.

For example, titanium fires can be put out with water, according to the CSB, but only if they are small fires. If there’s a large titanium fire, water can actually react with the metal and create explosive gas.

Fires like those caused by aluminum, titanium and other metal dusts should be combated with special Class D fire extinguishers designed for metal fires. These fire extinguishers use dry powders that absorb heat and cut off oxygen to flames. Safety managers should select an appropriate type of Class D extinguisher for the metals present in their facilities. (A variety of types exist for dealing with different metals; sodium chloride extinguishers are typically used for metals like aluminum, titanium, zirconium and magnesium.)

Combustible Dust Regulations

Although OSHA has been working on creating a comprehensive combustible dust standard since 2009, this process for developing and implementing a new standard hasn’t yet been completed. Despite this delay, OSHA can issue citations related to combustible dust under its General Duty Clause. Businesses are also required to comply with the NFPA’s standards related to combustible dust, which are enforced by local fire marshals. For more information about regulations, consult our Combustible Dust 101 post. 

Dust may seem like a harmless problem, and accidents may occur less frequently than those related to other workplace hazards, but the magnitude of these accidents is evidence that workplaces and regulators both need to pay more attention to combustible dust.

For more information about preventing combustible dust issues at your facility, take a look at this SlideShare: 

dust hazards


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