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It’s getting hot out there, so check your work/rest cycle

By Robert Goetz | 502nd Air Base Wing Public Affairs | April 24, 2017

JOINT BASE SAN ANTONIO-RANDOLPH, Texas — Email and pop-up messages that alert military members and civilian employees at Joint Base San Antonio about heat conditions could soon be appearing with regularity on their computers.

The messages relay the wet bulb globe temperature index – a measurement of air temperature, air movement, relative humidity and radiant heat – and the accompanying flag conditions that play an important role in mission safety.

“The JBSA command post sends out emails of the WBGT index and flag condition to make personnel aware of the work/rest cycles depending on their workload and the recommended water intake for that hour to prevent heat stress injuries,” said Maj. Tho Tran, 359th Aerospace Medicine Squadron Bioenvironmental Engineering Flight commander.

Every day during the warmest months of the year, a flight member – along with counterparts at other JBSA locations – takes an instrument called the thermal environment monitor outside to measure the WBGT. Measurements are tracked throughout the day via a remote display in an indoor location.

“There are three components to the monitor,” said Airman 1st Class David Flint, 359th AMDS Bioenvironmental Engineering Flight technician. “The black dry globe measures radiant heat, the white wet bulb measures humidity and air movement, and the white dry bulb measures the ambient air temperature.”

The WGBTs and corresponding flag conditions are 82-84.9 degrees for green, 85-87.9 degrees for yellow, 88-89.9 degrees for red and 90 degrees and above for black.

The readings are typically relayed to the JBSA command post when they reach the green flag condition and above, Flint said.

Flag conditions are recommendations for commanders and other supervisors to observe work/rest cycles and to enhance awareness of heat conditions and monitoring for signs of heat illness.

Air Force Instruction 48-151, which governs the Thermal Injury Prevention Program, provides guidelines for work/rest cycles and water intake based on workload and flag conditions.

For black flag conditions, the recommended work/rest cycles for acclimatized individuals are 50 minutes/10 minutes for easy work, 20 minutes/40 minutes for moderate work and 10 minutes/50 minutes for hard work. The recommended water intake for all workloads during a black flag condition is 1 quart per hour.

Flag conditions are especially critical for employees who work in open hangars and on the flightlines, firefighters, security forces members, groundskeepers and anyone else who works outside, as well as for Airmen taking part in physical training and those who exercise outdoors, Flint said.

Apparel is another consideration, he said.
“Firefighters’ suits add 10 degrees, so their work cycles will be different,” Flint said. “The same goes for security forces, whose body armor adds 5 degrees.”

Flag conditions “keep the mission going,” he said.
“These guidelines let people know how long they can work before they rest and how they have to hydrate,” Flint said.