MONROE — A sprinkler system was crucial to controlling an explosion and fire early May 9 at RR Donnelley, 350 17th St., said Monroe Fire Chief Dan Smits.

No one was in the 250,000-square-foot printing facility when a compressor exploded at about 1:30 a.m., Smits said. The explosion damaged duct work and some windows and caused the compressor to start on fire.

It also activated the sprinkler system, which contained the fire and minimized damage.

“The sprinkler system was right above the compressor. It did a wonderful job,” Smits said. Each sprinkler head has a glass bulb that melts at a specific temperature, allowing water to flow out.

Only one sprinkler head activated in this case, Smits said. He noted that it’s rare for all sprinkler heads to go off at once and drench everything, as is often depicted in movies.

“In close to 98% of fires, only a couple of heads go off. A lot of people have this vision that the building is floating down the street,” Smits said. In reality, “it’s not a lot of water.”

Smits credited the sprinkler system with protecting firefighter lives and containing “what could have been a very large and dangerous event.”

According to Smits, it appeared RR Donnelley had sufficient backup equipment to avoid a closure. A call to the business was not immediately returned.

Firefighters were on scene until about 4 a.m. The cause of the explosion was still under investigation.