In this chapter, the following terms have the meanings indicated. Terms Defined. “Acclimatization” means the body's temporary adaptation to work in heat that occurs as a person is exposed over time. “Alternative cooling and control measures” means engineering, work-practice, administrative, or other controls to manage heat, including job rotation, mechanical ventilation systems, misting equipment, cooling vests, air-cooled or water-cooled garments, and access to recreational water. “Drinking water” means potable water that is safe to drink and cool in temperature. “Emergency operations and essential service” means work in connection with an emergency that requires the involvement of law enforcement, emergency medical services, firefighting, rescue and evacuation operations, or emergency restoration of essential utilities or telecommunications. “Heat index” means a measure of how hot it feels when relative humidity is taken into account along with the actual air temperature, which can be extrapolated from temperature and relative humidity using the National Weather Service Heat Index Calculator. “High-heat conditions” means working conditions where the heat index of the work area equals or exceeds 90 degrees Fahrenheit. “Shade or shaded areas” means blockage of direct sunlight.