When volunteer firefighters were rushing to a blaze at a fertilizer plant in the town of West, Texas, earlier this week, they no doubt knew the dangers they would be facing but carried out their duties anyway, relying heavily on the training they'd received to deal with such situations.

The burning building contained huge quantities of explosive ammonium nitrate, an ingredient in the production of fertilizer.

Within two hours, a blast demolished the factory, levelled nearby buildings, killed at least 14 people and injured many more. According to The Associated Press, West Mayor Tommy Muska said 10 of the dead were first-responders, including five from the West Volunteer Fire Department and four emergency medics.

Robert Ursano, director of the Centre for the Study of Traumatic Stress in Bethesda, Md., said a combination of personal characteristics and preparation would have propelled them into harm's way.

While there's "a high degree of self-sacrifice involved in those kind of jobs," he said by phone Wednesday, emergency workers must undergo rigorous training that can "change our natural response" when a disaster strikes.

Self-sacrifice is a quality often celebrated in the aftermath of disasters. As rescue crews sifted through the rubble of the exploded factory in Texas on Wednesday,  U.S. President Barack Obama paid tribute to a different group of emergency workers 3,000 kilometres away, who had helped save lives in the aftermath of the Boston Marathon bombing.

"You displayed grit. You displayed compassion. You displayed civic duty. You displayed courage," Obama said during a memorial service at Cathedral of the Holy Cross in Boston. "And when we see that kind of spirit, there’s something about that that's infectious."

"Our thoughts, our prayers are with the people of West, Texas, where so many good people lost their lives, some lost their homes, many were injured, many are still missing," Obama said during a news conference Friday, after he issued an emergency declaration and pledged federal disaster relief aid to help West recover.

'You displayed grit. You displayed compassion. You displayed civic duty. You displayed courage.'  —U.S. President Barack Obama

Bruce Ramsay, a retired firefighter from North Vancouver and a traumatologist with the Justice Institute of British Columbia, said first responders are often very dedicated people who have "high control needs," meaning they value being in command of a situation.

Through training, emergency workers learn how to better suppress their emotions while at the scene of an emergency, he said, allowing them to operate in face of danger.

Through repetition police, firefighters, soldiers and EMS workers have their training "drilled in" to them "so that it becomes almost automatic," Ramsay says.

So in a moment of crisis, when instinct takes over, they're more likely to react professionally.

Response caught on film

A great example of this was captured in an iconic image taken in the moments after the Boston Marathon attack, Ursano said. It shows an elderly runner on the ground, with three police officers standing above him, a cloud of smoke at their backs.

In such an event, police "want to look to the outside, look to see where the threat is. If you just focus on the event, then you're going to miss what's happening behind and around you," he said.

si-boston-runner-04290691

Police officers react to an explosion at the finish line of the Boston Marathon in Boston on Monday. (The Boston Globe, John Tlumacki/Associated Press)

"Where we would have turned to the bomb, we'd be focused on it … these folks had turned in the other direction."

Both Ursano and Ramsay also emphasized the importance of helping first responders deal with the any psychological after-effects of working through a major emergency like the Texas explosion or the Boston attack and manhunt.

That can mean encouraging them to talk about the experience and stop suppressing their emotions once a dangerous situation has passed and they no longer have to rely so heavily on survival instincts.

"You kind of have to look at this as emotional first aid, just like a Band-Aid is to surgery," Ramsay said.

With files from The Associated Press