The number of grain dust explosions in the U.S. fell to a 10-year low in 2016, but two of the incidents resulted in the first fatalities reported since 2013, according to an annual report released by Purdue University’s department of agricultural and biological engineering.

There were five grain dust explosions in 2016, which compares to eight in 2015 and a 10-year average of 9.2 per year. Reported causes of ignition last year included sparks, possibly generated by static electricity or friction between machine parts, and overheated bearings, such as those on conveyor belts and elevators. One of the explosions occurred in a feed mill, two in grain mills and two in grain elevators.

Grain dust was confirmed as the main source of fuel in three of the incidents but could not be confirmed in two of the others. Fine particles or powder from the grain can also contribute to fires and explosions, said Kingsly Ambrose, assistant professor of agricultural and biological engineering at Purdue.

Two of the three fatalities in 2016 were from Indiana, and the third was from Georgia. Eight people were injured nationwide.

“The two most important factors in preventing an explosion are keeping the facilities clean and the equipment in good working condition,” Ambrose noted. “If the facility is clean, then the amount of potential fuel is minimized. If the equipment is in good working condition, there is less chance of ignition.”

Performing regularly scheduled equipment maintenance is a key first step in preventing fire and explosion. “We can be happy that the number of explosions is down, but it’s important to stay vigilant,” Ambrose said. “I always tell people to keep their eyes, nose and ears open: If you see something strange, hear an odd noise or smell something unusual, then that’s the time to shut down and check all the equipment.

“It’s not about completing a one-day maintenance and thinking you’re done for the year; it’s a constant, ongoing process,” he added.

The full report is available at http://bit.ly/2016Dust.