YUMA PROVING GROUND, Ariz.-- It's hot out there.American Soldiers need equipment that works exactly as it should anywhere in the world they are called upon to serve, and for most of its 75 year history U.S. Army Yuma Proving Ground (YPG) has subjected virtually every piece of equipment in the ground combat arsenal to the most punishing testing possible in an extreme desert environment.The testers of this equipment want to subject it to realistic use in the most extreme climate conditions possible--to the point of breaking the item, if it comes to that. But no matter what, YPG wants to protect the personnel engaged in this inherently dangerous endeavor."We have a mission that has to be done," said Wayne Schilders, weapons operation chief. "On the hottest days, we look at ways to mitigate it, such as starting earlier in the morning, increasing breaks in the hottest parts of the day, or rotating other workers in. The weather does not stop us from doing even the most strenuous missions."Planning to mitigate extreme heat is a routine event at YPG--last year, Yuma had more than 100 days in which the temperature exceeded 100 degrees Fahrenheit, and 175 in which the temperature was at least 90 degrees Fahrenheit. YPG personnel pay particular attention to the heat index and the wet bulb globe temperature (WBGT), which estimates the effect of the combination of temperature, humidity, wind speed, and solar radiation on humans. With every increase of the WBGT above 78 degrees, mitigations that impose a strict work-rest cycle go into effect and are strictly adhered to."Every time the heat index goes up, they take more breaks: either in the shade or into an air conditioned vehicle, out of the direct sunlight," said Mike Demcko, safety director.Demcko notes that following the work-rest cycles are vital to protecting the workforce, in the short and long term."Once you have severe heat exhaustion or heat stroke, your body becomes a lot more susceptible to it in the future," said Demcko.The proof of the success of YPG's heat safety program, Demcko said, is in the fact that the proving ground has not had a reportable heat injury since 2012. The year prior to this, the busiest in proving ground history in terms of direct labor hours, the installation had 21 reportable heat casualties, including two who were hospitalized.The people most susceptible to heat injury are those who are not accustomed to the extremes of Yuma's summers. Demcko said that proper acclimation to a desert environment takes two weeks on average. Further, the desert Southwest's dry heat can be insidious to people from other parts of the country and globe who equate overheating with excessive sweating."We have to make extra effort to watch out for our visitors," said Schilders. "Most of our higher headquarters personnel and representatives from program management offices are from the East Coast and are not acclimated to the extreme heat. Proper acclimation is key to avoiding heat injuries."The keys to successfully coping with the heat tend to be relatively simple. Water and ice are precious and vital commodities for testers on YPG's ranges, as are portable pop-up tents."They are one of the best things we have gotten our hands on," said Schilders. "Years ago we didn't have these--we had to use wooden shades we moved with a wrecker."The work conditions are extreme, but the personnel who do it month after month, year after year, take it in stride."It's rough in the summer, but you learn to cope with it," said Steven Allen, gun crew leader. "That's the nature of being a hot weather test facility: when it's hot, the customers pile on."For many range workers, however, the conditions of their job mean that the temperatures they are routinely exposed to are dramatically higher than the ambient temperature. This is particularly true for folks who test ground combat vehicles."It's generally 140 degrees plus inside of a turret when we're on our missions," said Tom Counts, lead engineering technician. "When you open the hatches while running missions, you get a lot of dirt. If you close the hatches, you get less dirt but more heat.""It's a lot like being in a tin shed if you're in the back of the vehicle," added Chris Ades, engineering technician. "The metal retains the heat. Even after the sun goes down, it will be hot to the touch for a few hours."Even more miserable are the times when the testers must wear the same body armor, face masks, or other gear that Soldiers don when using the vehicle in theater."They're not made to be comfortable," said Counts. "They're made to keep you awake and on guard to do what you have to do."YPG's sterling safety record in an extreme environment while engaged in inherently dangerous work is primarily a result of a deeply-ingrained safety ethos in all areas and all levels at the proving ground."You have to make sure you have a safety culture, and the way you do that is with leadership and worker buy-in," said Jaysen Lockett, safety manager for Trax Test Services. "What we do here is very important to the Warfighter. If we don't keep our employees safe all the time, then we're not successful and the Warfighter is negatively impacted.""We are all thinking about the long-term viability of the workforce," added Schilders. "You don't want to lose employees with years or decades of specialized experience and skills. It is incumbent upon us to ensure everyone's well-being in a hostile natural environment."