Environment and HF

1. Environment and HF INSY3020/7976/ENH670

2. Light – Radiant energy that is capable of exciting the retina of the eye and producing a visual sensation. Luminance – the amount of light leaving a surface; may be emitted or reflected; measured as luminous intensity per unit area (cd/m2)-(Radiance) Luminous Intensity – luminous flux per unit solid angle; expressed in candelas (cd) 1 cd source emits 12.75lm; also known as candle power Luminous Flux – the rate at which light energy is emitted or reflected from a source, expressed in lumens (lm) Illuminance – the amount of light striking a surface; measured in terms of luminous flux per unit area; (Irradiance)

3. Illumination Levels and Performance Implications • Higher levels of illumination improve visual performance • More difficult the task, the smaller the beneficial impact illumination has on reducing task completion time • Increasing illumination can also increase glare • High central task illumination degrades peripheral detection

4. Age and Visual Environment Elderly people (65+) require higher levels of illumination Glare sensitivity increases with age Elderly have greater difficulty matching and discriminating colors Adaptation of changing illumination levels takes longer

5. Visual Comfort Probability Index (VCP) • inversely related to direct glare • standard data provided with luminarie (i.e. lights) • data include tables of luminaire’s visual comfort probability ratings for various room geometries • provides an indication of the percentage of people in a given space that would find the glare from a fixture acceptable

6. To Reduce Direct Glare • use luminaires with low discomfort glare ratings (high VCP index) • avoid high intensity sources within 60 degrees of the center of the visual field • use shields, visors, hoods, diffusing lenses or screen filters • use indirect lighting • use several low intensity light sources • reduce the luminance ratio

7. To Reduce Reflective Glare • use diffuse lighting (soft light, diffusing lenses) • use dull, matte, non-polished surfaces (desktops) • make work surfaces adjustable (height and angle) • use indirect lighting to control all reflections • paint walls with dark colors, dull or matte finishes only • place computer screen on an adjustable cantilever arm • install the computer screen at right angles to any nearby windows

8. Climate Methods of heat exchange • Metabolic – • Evaporation – • Convection – • Radiation – • Conduction –

10. WBGT Index (°C) A – Acclimatized U- Unacclimatized L – Light H - Heavy M – Moderate V – Very Heavy W-Work R- Rest

11. Heat Stress Related Illnesses • Hypothermia – • Hyperthermia – • Heat Rash • Transient Heat Fatigue • Heat Syncope • Heat Cramps •  Heat Exhaustion •  Heat Stroke

12. Heat Rash (prickly heat) Cause: Heat buildup in the skin due to clogged pores and sweat ducts. Prolonged skin wetness from sweating Symptoms: Area becomes reddened and may itch or hurt. Skin eruptions. First Aid: Practice good personal hygiene to keep the skin clean and the pores unclogged. Allow skin to dry. Seriousness: Relatively minor.

13. Transient Heat Fatigue Cause: Loss of fluids reduces circulatory efficiency. Symptoms: General feeling of tiredness or fatigue. First Aid: Fluid replacement and rest. Seriousness: No long-term adverse effects.

14. Heat Syncope Cause: Circulatory system degradation that results in blood “pooling” in the lower extremities causing ischemia Symptoms: Fainting First Aid: Lay victim in a shady spot horizontally with feet elevated. If conscious, give fluids. Treatment is the same as that for shock. Seriousness: 1-2 Days Recovery

15. Heat Cramps Cause: Loss of important electrolytes in the blood and muscle tissues. This loss is due to excessive amounts of “salts” being lost in the victims sweat. Symptoms: Cramping of either voluntary (skeletal) muscles or involuntary (principally abdominal) muscles (or both). First Aid: Replenish electrolytes through drinking of fluids Seriousness: Debilitated for several days

16. Heat Exhaustion Cause: Depressed condition of the circulatory system due to dehydration. Symptoms: Nausea, dizziness, weakness headache, blurred vision, profuse sweating, cold/wet/grayish skin, unconsciousness, coma and death. First Aid: Place victim in a prone position in a cool, shady location, administer fluids if the victim is conscious, Seek medical care or transport to a hospital. Seriousness: several days to several weeks

17. Heat Stroke Cause: The body’s thermo-regulatory mechanism, located in the hypothalamus, fails and sweating ceases. Core temperature rises dramatically. Symptoms: Chills, restlessness, irritability, euphoria, red face and skin, disorientation, hot/dry skin (not always), collapse, unconsciousness, convulsions and death. First Aid: Immediate, aggressive cooling of the victim’s body. Transport to hospital Seriousness: Life Threatening

18. Heat Stress Risk Factors and Controls Personal Characteristics - very small body size, poor nutrition, overweight, poor physical condition, lack of heat-acclimatization, increasing age over 40, previous heat illness, late stages of pregnancy, diarrhea, vomiting, infections, fever, heart disease, high blood pressure, diabetes, sunburn, skin diseases, liver kidney and lung problems Environmental Factors - lack of air movement, temperatures above 70° F in daylight, temperatures above 70° F at night, direct sun light, humidity, exposure to toxic agents including pesticides

19.  Job Factors - heavy work, prolonged shifts, insufficient work breaks, work with or around heat generating machinery / equipment (e.g. blast furnace) • Clothing / Protective Gear Factors - thick clothing, more than one layer of clothing, tight clothing, stiff clothing, wearing darker colors, chemical resistance garments, using respirators • Behavioral Factors- - failure to drink sufficient water before work, during breaks, or after work, low salt diet, general fatigue or lack of sleep, excessive consumption of caffeine, alcohol consumption in the previous 24 hours, recent immunization or inoculation, illegal use of drugs, taking sleeping pills or other medications that limit sweating such as Atropine, Scopolamine, antihistamines, some tranquilizers, cold medicines, anti-diarrhea medicines, blood pressure medicines, diuretics, water pills, or amphetamines.

20. Hyperthermia Effects on Performance • Decrease in physical endurance – decrease work output under hyperthermic conditions • Simple reaction time – little effect on RT to visual and auditory stimuli • Choice RT – some evidence that performance may be impaired, especially after the task has been performed for some time • Tracking – impaired at temperatures >30 oC • Vigilance- optimal range being between 27 to 32 oC • Unsafe work behaviors above (63-73 oF) • Short-term memory – possible impairment • Complex problem solving – conflicted results

21. Hypothermia Effects on Performance • Decrease in strength and endurance • Tactile sensitivity – discrimination impaired below 4.4 oC • Manual dexterity –fine manipulative movements directly and indirectly impaired • Tracking performance – show decrements in cold temperatures • RT – simple RT appears to be relatively unaffected but there is evidence that choice RT is more vulnerable • Motivation – adversely affected