Chapter 11 Thermal Stressors

Thermal Stressors Ch 11 Pg 323 What are the signs and symptoms of heat stress?

1. Heat Rash - this is when skin remains moist with sweat for too long (unable to evaporate). Red irritated skin. 2. Heat Cramps - this is when profuse sweating, and lots of hydration with water leads to an unbalance of electrolytes in the body. Muscle cramps, pain, weakness. 3. Heat Syncope - Fainting as a result of heat exposure. Overheating without enough water or electrolytes. Blurred vision, fainting, and a normal body temperature.

Thermal Stressors Ch 11 Pg 331 What are some ways to prevent heat stress injuries?

1. Learn the signs and symptoms 2. Train workers 3. Perform heaviest work in coolest part of day 4. Acclimation of employees 5. Use the buddy system 6. Adequate fluid replacement 7. Light, loose-fitting clothes. 8. Work/rest cycle 9. Avoid caffeine and heavy meals, alcohol 10. Wear appropriate PPE.

Thermal Stressors Ch 11 Pg 321 Name the four basic sources of heat to the body.

1. Radiation - directly from light. 2. Convection - directly from a medium (air, water, etc.) 3. Conduction - directly from physical contact with an object. 4. Metabolic - internally generated heat from chemical reactions in the body.

Thermal Stressors Ch 11 Pg 328 If an employee averages 4.33 kcal/min metabolic rate in an 8 hour shift, what is the employees workload? Reference: Light work: up to 200 kcal/hr ; Medium work: 200-350 kcal/hr ; Heavy work: 350 - 500 kcal/hr.

4.33 x 60 = 259.8 kcal/h = medium work.

Thermal Stressors Ch 11 Pg 330 An employee has a moderate workload and an average Wet-Bulb Globe Temp (WBGT) of 84.44 F. Using the OSHA Heat Exposure Threshold Limit Value chart , what is the appropriate work/rest schedule for this employee? % Work Workload Light Moderate Heavy 75 to 100% 31.0°C 28.0°C N/A 50 to 75% 31.0°C 29.0°C 27.5°C 25 to 50% 32.0°C 30.0°C 29.0°C 0 to 25% 32.5°C 31.5°C 30.5°C

84.44 F ~ 29 C = 50% to 75% work. Recommended work/rest schedule would be either 30 mins work 30 mins rest or 45 mins work 15 mins rest.

Thermal Stressors Ch 11 Pg 332 What is Chilblains, what are the signs and symptoms, and what are preventative measures?

AKA pernio is itchy and tender red or purple bumps that occur as a reaction to cold temperatures. This happens when the blood vessels shut down, typically occur several hours after exposure. There is a familial tendency, and people with low body weight or poor nutrition are more affected. Insulated workplaces, warm clothing, keeping warm, exercising before going into cold weather, not smoking, etc.

Thermal Stressors Ch 11 Pg 337 Key Information What are the sources of heat?

Radiation, conduction, convection, metabolic.

Thermal Stressors Ch 11 Pg 337 Key Information What is radiant heat?

the amount of thermal radiation between two or more objects

Thermal Stressors Ch 11 Pg 327 What is the average metabolic rate for an employee who shovels gravel for 1.5 hours at a rate of 7.0 kcal/min, takes a break for 30 min in a sitting position (metabolic rate = 0.3 kcal/min), then constructs a concrete form for 4 hours (metabolic rate of 3.5 kcal/min) then pours and finishes the concrete for 2 hours (metabolic rate 5.0 kcal/min)? Use the formula Average Metabolic Rate = [(M1)(T1) + ...(Mn)(Tn)]/[(T1)+...(Tn)]

Average Metabolic Rate = [(M1)(T1) + ...(Mn)(Tn)]/[(T1)+...(Tn)] M1 = 7.0 kcal/min ; T1 = 1.5 h = 90 min M2 = 0.3 kcal/min ; T2 = 30 min M3 = 3.5 kcal/min ; T3 = 4 h = 240 min M4 = 5.0 kcal/min ; T4 = 2h = 120 min MR = [(7.0)(90) + (0.3)(30) + (3.5)(240) + (5.0)(120)]/(90 + 30 + 240 + 120) MR = (630 + 9 + 840 + 600)/(480) MR = 4.33 kcal/min

Thermal Stressors Ch 11 Pg 325 What are some control methods for heat stress?

Engineering Controls - ventilation, air conditioning, heat shields, insulation. Administrative Controls - Acclimation schedules, procedures to allow for increased breaks, rotational work assignments to avoid extreme temperatures, awareness campaigns. Work-Practice Controls - Fluid replacement, Work/rest cycles, exercise, eating light meals, etc. PPE - cooling vests, thermally resistant clothing, etc.

Thermal Stressors Ch 11 Pg 331 What are some safety problems related to cold stress?

Fatigue, distraction, difficulty performing work.

Thermal Stressors Ch 11 Pg 331 What are the two type of cold stress injuries, and what are some examples?

Freezing and non-freezing injuries. Freezing: Frost bite Non-freezing: chilblains, immersion injuries, hypothermia. Non-freezing injuries can occur when temperatures are above 32 F.

Thermal Stressors Ch 11 Pg 324 What is heat stroke?

Heat stroke is a severe medical emergency that occurs when the body's ability to thermoregulate fails and sweating becomes inadequate to cool internal temperature. If left untreated, organ and brain damage will occur, ultimately leading to death. A sustained body temperature above 104 F can cause heat stroke. Treatment must be quick and must focus on cooling internal temperature as quickly as possible. Ice baths are very common.

Thermal Stressors Ch 11 Pg 324 What is heat exhaustion?

Massive loss of fluids and salts from profuse sweating. Employees with heat exhaustion still sweat but can lose consciousness and become extremely weak. Pale face, low blood pressure, nausea, vomiting are all symptoms. A key note to remember is that people who have experienced heat exhaustion are more susceptible to it in the future.

Thermal Stressors Ch 11 Pg 334 What is hypothermia, what are it's three degrees, what are the signs and symptoms?

Hypothermia is a reduction of the bodies core temperature that can result in a potential deterioration of CNS, cardiac, and musculoskeletal functions. There are three degrees of hypothermia (mild, moderate, and severe). Mild: Core temp between 89.6 - 95F. Disorientation, disinterest in surroundings, voilent shivers. Moderate: 78.8 - 89.59F. Cardiac irregularities, corneal reflexes absent. Severe: Below 78.79F. V-fib, may appear clinically dead but still alive (thus the saying that no one is dead until they are warm and dead).

Thermal Stressors Ch 11 Pg 322 What is the human reaction to heat stress, and what are some of the safety issues associated with it?

Sweating, weakness, dizziness, disorientation in severe cases. Slippery palms, decreased alertness, discomfort and irritability, exacerbation of preexisting health problems.

Thermal Stressors Ch 11 Pg 334 What is Frostbite, what are it's four degrees, and what are its signs and symptoms?

Tissue damage from exposure to below-freezing temperatures. Speed, onset, and severity depend on length of exposure and temperature. Ice crystals form and puncture cellular walls, leading to cell death. When the tissue is frozen it appears "Dead white" and is hard or even brittle. First degree: similar to chilblains, increased blood flow, itching and edema (swelling). No blisters or peeling of skin. Second degree: blistering and desquamation (shedding of outer layers of skin). Third degree: necrosis of skin and subcutaneous tissue ulceration. Fourth degree: destruction of connective tissues and bone, accompanied by gangrene. Infections are common in these events.

Thermal Stressors Ch 11 Pg 333 What is an immersion injury (trench foot), what are the signs and symptoms, and what are preventative measures?

Trench foot is typically 12+ hours of exposure to low temperatures where persons remain immobile without access to dry footwear. The injury will appear cold, swollen, waxy-white with cyanotic burgundy-to-blue splotches and the skin is anesthetic and deep musculoskeletal sensation is lost. To prevent trench foot, keep feet dry and clean, replace socks daily, treat the affected part with heat pads, do not wear socks when sleeping, and obtain medical assistance if necessary.

Thermal Stressors Ch 11 Pg 329 An employee works at 79 F for 90 mins, 74 F for 30 mins, 86 F for 240 mins, and 88 F for 120 mins. What is the average Wet-Bulb Globe Temp (WBGT) for this employee? Use the formula WBGT (avg) = (WBGT1)(t1) +...(WBGTn)(tn)/(t1+...tn). For indoor conditions with no solar load WBGT is calculated as WBGT = 0.7WB + 0.3GT. For outdoor with solar load WBGT is calculated as WBGT = 0.7WB +0.2GT + 0.1DB where DB is dry-bulb temp.

WBGT avg = (WBGT1)(t1) +...(WBGTn)(tn)/(t1 +...tn) WBGT1 = 79 F ; t1 = 90 mins WBGT2 = 74 F ; t2 = 30 mins WBGT3 = 86 F ; t3 = 240 mins WBGT4 = 88 F ; t4 = 120 mins WBGT avg = [79(90) + (74)(30) + (86)(120) + (88)(120)]/ (90+30+240+120) WBGT avg = 40530/480 = 84.44 F

Thermal Stressors Ch 11 Pg 321 What is Heat Stress, and what are some of its sources?

When internal temperature of the body increases resulting in symptoms such as increased heart rate, sweating, dehydration, etc. Sources include recreational activities, working in high heat environments, failure to hydrate properly, taking certain medications while working in hot environments.

Thermal Stressors Ch 11 Pg 335 What is the wind chill for wind blowing at 20 mph and a temperature of 10 F. Use the formula: Wind Chill (F) = 35.74 + 0.6215T - 35.75(V^0.16) + 0.4275T(V^0.16) where T is air temperature (F) and V is wind speed (mph).

Wind Chill (F) = 35.74 + 0.6215T - 35.75(V^0.16) + 0.4275T(V^0.16) T = 10 F V = 20 mph WC = 35.74 + 0.6215(10) - 35.75(20^0.16) + 0.4275(10)(20^0.16) WC = -9 F