Post by momto4 on Sept 17, 2007 9:48:23 GMT -6
A google search on "productivity decrease temperature humidity" gives numerous links on this topic. The links demonstrate (to me anyway) that high temperature and humidity has a negative impact on everyone. We know that the effects can be worse for some.
Here are some excerpts from this Navy website about the effects of heat and humidity. This mentions heat above 30°C which translates to 86°F. This is of course talking about adults in good physical shape in a work environment.
www.safetycenter.navy.mil/acquisition/heatstress/default.htm
Effects of Heat Exposure
Direct and Indirect Impacts on Safety and Productivity
Uncontrolled heat stress conditions can lead to heat-related illnesses, disabilities, and even death. A direct impact on work environments with poorly controlled heat stress conditions is reduced work capacity, and in extreme cases, the need for additional manpower to accomplish a given set of tasks. This can have a significant, but often unappreciated, impact on life-cycle costs for manpower and decreased productivity over the life of a system. Heat stress impacts on safety and productivity can be attributed to the following:
Reduced Mental Acuity
In moderately hot environments, the body "goes to work" to get rid of excess heat so it can maintain its normal body temperature. The heart rate increases to pump more blood through outer body parts and skin so that excess heat is lost to the environment, and sweating occurs. Sweating is the body’s natural mechanism to regulate body temperature via evaporative cooling. In hot, humid conditions evaporation of sweat and its cooling effect are limited. Personal protective equipment, such as welding protective equipment or firefighting ensembles often further impair the body’s natural ability to cool itself by limiting the evaporation of sweat. These changes impose additional demands on the body. Changes in blood flow and excessive sweating reduce a person's ability to do physical and mental work. Manual work produces additional metabolic heat and adds to the body’s heat burden. When the environmental temperature rises above 30°C, it may interfere with the performance of mental tasks. In many cases, mental acuity may decline before the ability to perform rote physical tasks is impaired.
Decrease in Physical Work Capacity
The human body must maintain a long-term balance between energy exchange with the external environment and “internal” heat load created by basic metabolism (energy used for basic functions) and physical work. If such a balance cannot be maintained, increase in internal body temperature can lead to serious and often rapid safety impacts. Where the external heat load cannot be fully controlled, long-term balance is maintained by reducing workload. People will naturally devote an increased fraction of time to rest and less to physical labor. Health and safety precautions developed by the military, partially in response to serious incidents, require a specific work-rest cycle based on the environmental heat burden, workload, and protective equipment required. Physiological Heat Exposure Limits (PHEL) and Physical Activity Physiological Heat Exposure Limits (PHELs) provide a series of curves reflecting the period of allowable exposure under particular conditions (see diagram from link). The PHEL employs an effective temperature index (the Wet Bulb Globe Temperature), which provides a single number combining the effects of temperature, humidity, radiant heat and airflow with the level of activity to create a relatively simple tool, illustrated in the chart below. More detailed information is available in OPNAVINST 5100.19 , Chapter B2- Heat Stress.
Increase in Mishaps
Discomfort, reduced mental acuity, and decline in attention to detail may increase the likelihood of error and associated mishaps. Heat and humidity can also lead to accidents resulting from the slipperiness of sweaty palms and to accidental contact with hot surfaces. As a worker moves from a cold to a hot environment, fogging of eyeglasses can briefly obscure vision, presenting an additional safety hazard.
Potential Medical Effects
A range of physical symptoms of varying severity have been associated with heat stress. As with most medical effects, risk varies with a range of personal and environmental factors. These include individual tolerance, personal acclimatization, fatigue, and prior activities that affect water balance such as consumption of alcohol or caffeinated beverages. Click on one of the following major medical effects of heat stress for more information:
Heat Stroke
Heat Exhaustion
Heat Cramps
Heat Rash
Recommendations
According to the Manual of Preventive Medicine, Ch 3, Ventilation & Thermal Stress Ashore & Afloat, the upper thermal design limits within the living compartments, recreation spaces, mess decks (excluding serving lines), sick bay and inpatient wards, operating rooms and intensive care spaces, administrative areas, control, and all operating electronic spaces aboard surface vessels should not be more than 80° F dry bulb (DB) temperature, 68° F wet bulb WT, 55% relative humidity (RH), with 72° F wet bulb globe temperature (WBGT). The new Navy ships, such as DD(X) and LCS, are being designed for interior air conditioned temperatures of 78° F DB, 65° F WB (50% RH). These new interior temperatures fall within industry accepted standard comfort levels as determined by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). A preferred WBGT of 78° F applies to prescribed hot-weather operational conditions in: laundries, galleys, sculleries, passageways not open directly on weather decks, and food serving lines.
Conclusion
Heat stress conditions have significant impacts on safety and productivity aboard ships. Heat stress can lead to heat-related illnesses, disabilities, and even death. Sustained high temperatures leading to heat stress conditions can lower work performance and morale and impair mental alertness, increasing the risk of workplace accidents, and ultimately compromising the readiness of the ship. Moreover, heat stress directly impacts manpower requirements aboard ship when heat exposures are high enough to require work-rest rotations.
Designing for proper temperature control and utilizing better technology to avoid or reduce heat stress conditions aboard ship will result in Sailors performing their duties in a comfortable and efficient manner. Designs that control or eliminate heat stress conditions will reduce the need for additional manpower (thereby reducing costs) and will improve shipboard safety, productivity, and quality of life.
Here are some excerpts from this Navy website about the effects of heat and humidity. This mentions heat above 30°C which translates to 86°F. This is of course talking about adults in good physical shape in a work environment.
www.safetycenter.navy.mil/acquisition/heatstress/default.htm
Effects of Heat Exposure
Direct and Indirect Impacts on Safety and Productivity
Uncontrolled heat stress conditions can lead to heat-related illnesses, disabilities, and even death. A direct impact on work environments with poorly controlled heat stress conditions is reduced work capacity, and in extreme cases, the need for additional manpower to accomplish a given set of tasks. This can have a significant, but often unappreciated, impact on life-cycle costs for manpower and decreased productivity over the life of a system. Heat stress impacts on safety and productivity can be attributed to the following:
Reduced Mental Acuity
In moderately hot environments, the body "goes to work" to get rid of excess heat so it can maintain its normal body temperature. The heart rate increases to pump more blood through outer body parts and skin so that excess heat is lost to the environment, and sweating occurs. Sweating is the body’s natural mechanism to regulate body temperature via evaporative cooling. In hot, humid conditions evaporation of sweat and its cooling effect are limited. Personal protective equipment, such as welding protective equipment or firefighting ensembles often further impair the body’s natural ability to cool itself by limiting the evaporation of sweat. These changes impose additional demands on the body. Changes in blood flow and excessive sweating reduce a person's ability to do physical and mental work. Manual work produces additional metabolic heat and adds to the body’s heat burden. When the environmental temperature rises above 30°C, it may interfere with the performance of mental tasks. In many cases, mental acuity may decline before the ability to perform rote physical tasks is impaired.
Decrease in Physical Work Capacity
The human body must maintain a long-term balance between energy exchange with the external environment and “internal” heat load created by basic metabolism (energy used for basic functions) and physical work. If such a balance cannot be maintained, increase in internal body temperature can lead to serious and often rapid safety impacts. Where the external heat load cannot be fully controlled, long-term balance is maintained by reducing workload. People will naturally devote an increased fraction of time to rest and less to physical labor. Health and safety precautions developed by the military, partially in response to serious incidents, require a specific work-rest cycle based on the environmental heat burden, workload, and protective equipment required. Physiological Heat Exposure Limits (PHEL) and Physical Activity Physiological Heat Exposure Limits (PHELs) provide a series of curves reflecting the period of allowable exposure under particular conditions (see diagram from link). The PHEL employs an effective temperature index (the Wet Bulb Globe Temperature), which provides a single number combining the effects of temperature, humidity, radiant heat and airflow with the level of activity to create a relatively simple tool, illustrated in the chart below. More detailed information is available in OPNAVINST 5100.19 , Chapter B2- Heat Stress.
Increase in Mishaps
Discomfort, reduced mental acuity, and decline in attention to detail may increase the likelihood of error and associated mishaps. Heat and humidity can also lead to accidents resulting from the slipperiness of sweaty palms and to accidental contact with hot surfaces. As a worker moves from a cold to a hot environment, fogging of eyeglasses can briefly obscure vision, presenting an additional safety hazard.
Potential Medical Effects
A range of physical symptoms of varying severity have been associated with heat stress. As with most medical effects, risk varies with a range of personal and environmental factors. These include individual tolerance, personal acclimatization, fatigue, and prior activities that affect water balance such as consumption of alcohol or caffeinated beverages. Click on one of the following major medical effects of heat stress for more information:
Heat Stroke
Heat Exhaustion
Heat Cramps
Heat Rash
Recommendations
According to the Manual of Preventive Medicine, Ch 3, Ventilation & Thermal Stress Ashore & Afloat, the upper thermal design limits within the living compartments, recreation spaces, mess decks (excluding serving lines), sick bay and inpatient wards, operating rooms and intensive care spaces, administrative areas, control, and all operating electronic spaces aboard surface vessels should not be more than 80° F dry bulb (DB) temperature, 68° F wet bulb WT, 55% relative humidity (RH), with 72° F wet bulb globe temperature (WBGT). The new Navy ships, such as DD(X) and LCS, are being designed for interior air conditioned temperatures of 78° F DB, 65° F WB (50% RH). These new interior temperatures fall within industry accepted standard comfort levels as determined by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). A preferred WBGT of 78° F applies to prescribed hot-weather operational conditions in: laundries, galleys, sculleries, passageways not open directly on weather decks, and food serving lines.
Conclusion
Heat stress conditions have significant impacts on safety and productivity aboard ships. Heat stress can lead to heat-related illnesses, disabilities, and even death. Sustained high temperatures leading to heat stress conditions can lower work performance and morale and impair mental alertness, increasing the risk of workplace accidents, and ultimately compromising the readiness of the ship. Moreover, heat stress directly impacts manpower requirements aboard ship when heat exposures are high enough to require work-rest rotations.
Designing for proper temperature control and utilizing better technology to avoid or reduce heat stress conditions aboard ship will result in Sailors performing their duties in a comfortable and efficient manner. Designs that control or eliminate heat stress conditions will reduce the need for additional manpower (thereby reducing costs) and will improve shipboard safety, productivity, and quality of life.
