Chapter 11 - Thermal Stressors Flashcards
Heat stress
Increase in body temperature, heart rate, and sweating
Four sources of heat stress
Radiation, conduction, convection, and metabolic
Heat transfer
heat always moves from warmer to cooler place
Radiation heat
Amount of thermal radiation between two or more objects
Convection
process whereby thermal energy is transferred by movement of a heated fluid such as liquid or air
Conduction
transfer of thermal energy between two objects in contact with each other
metabolic heat
generated from within the body through work - has potential to overheat the body
Survival range for human body
97F-100F
To regulate body temperature (to rid body of excess heat)
- varying rate and amount of blood circulation through the skin
- heart pumps more blood, blood vessels expand, capillaries along upper layer of skin fill with blood- excess heat is lost to the cooler environment
- release of sweat from the glands
- sweat is evaporated eliminating heat from the body (humidity affects evaporation making it more difficult to cool)
Effects of heat stress
Increased blood at external surface of the body, less going to active muscles, brain and other organs
- strength declines, fatigue occurs, alertness and mental capacity also may be affected
Accidents due to heat
due to sweaty and slippery palms, dizziness, fatigue, decreased alertness, fogging of safety eye ware, irritability, anger, emotion
Heat exposure disorders
heat rash, heat cramps, heat syncope, dehydration, heat exhaustion, and heat stroke
Heat cramps
excessive sweat and hydration without adequate replacement of body salts
Heat syncope
Fainting as a result of exposure to heat- mild overheating with inadequate water or salt
blurred vision, fainting, normal body temperature
pooling of blood in the legs and skin from prolonged static posture an heat exposure
Heat exhaustion
loss of large amounts of fluid and salts from excessive sweating
extreme fatigue, weakness, blurred vision, dizziness, high pulse rate, profuse sweating, low blood pressure, pale face, clammy skin, collapse, nausea and vomiting, headaches, and slightly increased body temperature- may lead to stroke
lie down flat on their back in a cool environment, drink water cool their skin and loosen clothing
heat stroke
medical emergency- body temperature regulation system fails and sweating becomes inadequate or stops entirely- without treatment- death or brain damage
signs and symptoms- chills, restlessness, irritability, mental confusion, euphoria, red facce disorientation, hot dry skin, erratic behavior, unconsciousness, convulsions- temp greater than 104
Heat Control - Engineering Methods
General ventilation - to dilute hot air with cooler air
Air treatment / cooling- removes heat and humidity from air
Air conditioning -
Use of chillers to circulate cool water through air heat exchangers over which air from the ventilation system is passed - can also reduce air humidity
Convection fans - can increase heat exchange
Insulating hot surfaces or tools
Heat shields - separate workers from heat generation
Administrative/ Work Control Practices
Acclimation or acclimatization- gradual process - expose workers to approximately 20% on each day for five days - closely monitor new employees for heat-related injuries
Fluid replacement - equal to amount of sweat produced and with normal or near normal meals- caffeine not recommended
Work/ Rest cycles - Use WBGT Index
PPE- reflective clothing, auxiliary cooling- ice vests, water cooled garments, wetted terry cloth or cotton suits, wet scarf around the neck- sun block at least 15
Heat stress training
knowledge of hazards
recognition of predisposing factors, danger signs, and symptoms
awareness of first aid procedures and potential effects
employee responsibilities
use of PPE
physical fitness to prevent heat-related disorders
fluid replacement
dangers of drug and alcohol in hot work environments
purpose and coverage of environmental and medical surveillance programs
Heat stress prevention- additional measures
learning signs and symptoms
training workers about heat-related illness
perform the heaviest work during the coolest part of the day
acclimation of employees
use the buddy system
adequate fluid replacement (one cup water every 15-20min)
light loose-fitting breathable clothing
work/rest cycle
avoid caffeine and alcohol
PPE
Cold stress
heat loss through radiation, conduction, convection, and evaporation
Heat loss
Radiation- body heat loss to colder environments
Convection - body heat lost through direct contact with a cooler object
Convection- molecules against the surface of a warm body are moved away and replaced (wind chill example)
Evaporation- heat and fluid loss to the environment from sweating and respiration
Safety problems related to cold
cold-related injuries- non- freezing and freezing
Non-freezing- chilblains, immersion injuries, hypothermia
Freezing- frostbite
chillblains
pernio/perniosis- itchy tender red or purple bumps - a result of shutting down of blood vessels in cold conditions
contributing factors include familial tendency, peripheral vascular disease, low body weight or poor nutrition, hormonal changes, connective tissue disease, bone marrow disorders
little treatment- try to prevent secondary infection from scratching with steroidal cream
prevent chilblains with insulated workplaces, warm clothing, meds that constrict blood vessels, exercise before cold, cotton-lined waterproof gloves
Immersion injuries- trench foot
prolonged exposure to cold weather
the injured foot is cold, swollen, waxy-white, with cyanotic burgundy to blue splotches, skis is anesthetic and deep musculoskeletal sensation is lost
air dry and elevate feet, clean dry socks, warm packs for 5 minutes, do not wear socks when sleeping or resting, medical attention
hypothermia
reduction of body’s core temperature below normal - progressive deterioration in cerebral, musculoskeletal and cardiac functions
three stages- mild - violent shivering, virtual cessation of effective muscular activity, disorientation, and disinterest in surroundings 89-95
moderate - 78-89 - cardiac irregularities at 86, corneal reflexes absent below 82
severe- below 78 - may appear dead
Frostbite
cellular injury and death from cellular trauma due tot he formation of ice crystals and from complex vascular reactions in cold exposure
first degree- similar to chillblain
second degree - blistering and desquamation
third degree - necrosis of skin and subcutaneous tissue with ulceration
fourth degree - destruction of connective tissue and bones and gangrene
Frostbite prevention measures
observance and adherence to the wind chill factor
proper protective clothing - loose layered clothing, inner layer porous for airflow
proper nutrition and activity
fluid replacement or intake
training and discipline - physical conditioning, adequate personal hygiene, and signs and symptoms of cold-related injuries
