U.S. Department of Labor
Table of Contents
Heat Stress: Case History
Employees are to wear multiple layers of protective clothing and equipment such as welding hoods, leather welding jackets and heavy gloves. Body heat can become trapped under the layers of clothing.
A shipfitter who had been working inside a structural unit in an outdoor staging area was nearing the end of his workshift. The sun on the structural unit quickly heated the interior spaces. The shipfitter pushed himself to finish the job ahead of schedule. When he finished, his supervisors asked him if he would be willing to work overtime to help complete a job that was behind schedule. Without taking time to rest, cool down and rehydrate before starting the new job, the shipfitter carried his heavy tools to the other job site and began to work.
He had to climb ladders several times to access the new job site. The new job site was located on a unit that had been exposed to direct sunlight all day and was radiating heat. The shipfitter performed demanding alignment, welding, and grinding tasks for the next hour. When he stood up he felt dizzy and stumbled forward. The shipfitter dropped down on one knee, fell forward and hurt his hand when it hit a metal clip. Nearby employees came to the shipfitter's aid, removed some of his heavy protective clothing and gave him water to drink. The shipfitter's dehydration and heat exhaustion were serious enough that he had to be moved off the vessel section in a mobile man-lift and be taken to the shipyard medical clinic for evaluation.
Analysis and Preventive Measures
Cooling vests that weigh less than 5 pounds and maintain a 59°F temperature for up to 2 hours are available. These vests are designed for use under protective clothing. Although cooling vests may not be appropriate in every situation, they can reduce heat related risks for employees working in small and tight spaces where there is limited natural or mechanical ventilation.
Exposure to excessive heat can take a severe toll on shipfitters. Dehydration and heat stress can cause fatigue and disorientation. If this happens when an employee is performing a high risk task, such as climbing a ladder or walking near an impalement hazard, there is a risk of serious injury. Prolonged exposure also may result in heat exhaustion and heat stroke. Because hot environments are inevitable in shipfitting, it is essential that practical steps be taken to minimize the risk of heat stress so employees can maintain productive work practices. Where possible, providing ventilation and spot cooling by local exhaust ventilation can reduce the effects of heat on employees. Shading structures can be used to block out direct sunlight.
Work areas need to have adequate amounts of cool drinking water so employees don't risk becoming dehydrated. Employees need to be encouraged to drink 4 to 8 ounces of water or sports drink every 15 minutes while working in hot humid conditions. Rotating employees and providing periodic rest breaks can help employees cool down core body temperature and recover from heat-related fatigue. Educating employees to replace fluids lost through sweating and recognizing the symptoms of heat stress are essential to minimizing heat-related illnesses. Employees should also be cautioned about over hydrating. Limit fluid to no more than 1 ½ quarts per hour when working in hot humid conditions and no more than 12 quarts of fluid in a 24 hour period.