Agricultural Work in Cold Weather
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Transcript of Agricultural Work in Cold Weather
Agricultural Work in Cold WeatherQiuqing Geng, Ph.D
Robert Stuthridge, M.Sc.
Changing environment
Agricultural work in cold weather
32-50 °F; Wind speed < 0,4 m/s
Outdoor cold exposure Indoor cold exposure
Heat production = heat loss
The body (core) temperature should be maintained at 98.6 °F
Cold effect on human thermal balance
Heat production Heat loss
convection
radiationevaporation
conduction
food , rest & muscular work
Cold Environment
Cold environment = Conditions that cause greater than normal body heat losses:
The body responds to cold by:
• Low air temperature• Radiant temperature• High cool wind speed• Air humidity
• Constricting dermal blood vessels
• Shivering
Convection increases with higher wind speed, conduction occurs from hands to the cold spade and from feet to the ground
How do we lose heat in the cold?
Convection
RadiationEvaporation
Mode of heat loss
Climatic factor
Other factors
Convection Air tempWind speed
ActivitiesClothing isolation
Radiation Radiant temp Clothing Colour of surface
Conduction Surface temp Clothing Properties of
contact material
Evaporation Humidity Air temp
Wind speed
ActivitiesClothing
Conduction
Cold stress
Cold stress - thermal load on the body when abnormal heat loss is
anticipated and compensatory thermoregulatory actions are needed to maintain a thermally neutral state.
Cold and cold protection effects
on work
Hand temp.
Effects of temperature on manual function
°F90 - 97 Optimal hand and finger function
81 - 90 Effects on finger dexterity, perception and speed
68 - 81 Impaired performance in work with small details, reduced accuracy and endurance
59 - 68 Decrement in manual dexterity of gross hand/finger work, occasional pain sensation
50 - 59 Reduced gross muscle strength and coordination, pain sensation
< 50 Numbness, manual performance reduced to simple gripping, pushing etc., spontaneous rhythmic re-warming (Lewis reaction)
43 - 46 Loss of sensations and thermal receptors of superficial skin (nervous block)
≤ 32 Freezing of tissues
Cold effect on manual task performance
Cold injuries - Frostbite• Skin tissue is frozen. Freezing point of skin ≈ 32°F • Wind-chill accelerates process. • Contacting cold metal with bare skin can rapidly cause frostbite.
Frostbites in the ears are almost twice as common as that of
the nose and cheek.
Ears, cheeks. nose, hands, feet main injury sites.
You should be familiar with signs & symptoms of frostbite - see handouts.
Frostbites of the hands and feet more often cause severe tissue damage and
require medical treatment.
Cold injuries - HypothermiaCore body temperature <95ºF due to prolonged exposure to cold and damp conditions.
• Most cases: air temp. 30 to 50°F;• Can occur in air temp. to 65°F,
particularly if clothing is wet;• Can occur in water temp. to 72°F.
Signs & symptoms of hypothermia - see handouts
Cold injuries - Non-Freezing Cold Injuries (NFCI)
NFCI: cold & wet conditions above freezing (~32-39F) and immobilization causes venous stagnation. Legs/feet e.g. trench foot
Other cold related injuries:
Signs & symptoms of NFCI - see handouts
trench foot
Slips and falls Strains, sprains, etc.
0 10 20 30 40 50 60 70 80 90 100-40
-30
-20
-10
0
10
20
30
40
Contact time (s)
Surf
ace
tem
pera
ture
(°F)
Numbness threshold, t(45)
Alum.
Steel
Nylon
Wood
Numbness threshold: surface temperature of the material as a function of contact time for TC to reach 45°F (range of TS from –40 to 40 °F, time limited to < 100 sec)
Cold-related diseases
Cold -related diseases are either caused by cold or their symptoms are aggravated by exposure to cold .
•Cardiovascular diseases;•Respiratory diseases;•Diseases in peripheral circulation;•Musculoskeletal diseases.
Male death rates due to cold are greater than the rates for females.
REDUCING COLD INJURY RISK
• Organizational measures
• Technical measures• Protective clothing• Protection of
extremities• Other measures
REDUCING COLD INJURY RISK Organizational measures
• Check weather conditions; • Work indoors;• Protective clothing;• Extra help - complete jobs faster;• Allow more time per task - work-rest
regimens must reflect task, workload, & protection levels;
• Reliable communication system; • Flexibility re: intensity/duration of work; • Frequent breaks (hot drinks/food in
heated shelter); • Sufficient time for recovery after
severe exposures;
• Choose equipment intended for cold conditions;
• Store equipment in protected, preferably heated space, or pre-warm before use;
• Insulate metallic handles/controls (rubber, plastic, wood);
• Allow operation by gloved hands;• Slip resistant handles;• Repair/maintain indoors or
prepare for easy repair/maintenance in adverse conditions
REDUCING COLD INJURY RISK Technical measures
• Avoid slippery materials and materials with different friction qualities in the same space;
• Inclination of ground - water to drain away
• Remove ice and snow from entries, passages, working floors and machinery steps;
• Sand or salt walkways regularly;• Openings in floor covered up or
guarded;• Warning signs, if surfaces are slippery;• Shoes - anti-slip soles, anti-skid
devices.
REDUCING COLD INJURY RISK Technical measures
The need for thermal insulation (clo-value); Wear at least three layersBasic insulation value of clothing - only for static (resting), wind-still conditions (after ISO-TR 11079). Wind increases convective heat loss.Clothing ensemble (Three-layer ensembles) Insulation (clo)Underpants,undershirt, shirt, trousers, jacket, overjacket, overtrouser, socks, shoes
1,9
Undershirt, underpants, insulated trousers, insulated jacket, overtrousers, overjacket, socks, shoes, hat, gloves
2,6
Undershirt, underpants, insulated trousers, insulated jacket, overtrousers and parka with lining, socks, shoes, hat, mittens
3,4
Undershirt, underpants, insulated trousers, insulated jacket, insulated overtrousers and parka with thick lining, socks, shoes, hat, mittens
4,2
Arctic clothing systems 3,0 – 4,5
REDUCING COLD INJURY RISKProtective clothing
Multilayer clothing more flexible than fewer, thicker layers.
1. Underwear provides humidity & moisture control at skin surface; 2. Intermediate layers mostly deliver thermal insulation. 1 to 3
garment layers, depending on environmental conditions, physical activity and thermal properties of each layer;
3. Outerwear protects against wind, water, dust and other factors.
Important! Friction between layers. Textile materials with high internal friction may restrict movement.
REDUCING COLD INJURY RISK Protective clothing
50 32
14
-4
-22
-40
-58
-76
(F)
Time limits for light and moderate
work with two insulation levels of clothing
• Up to 40% of body heat can be lost if head exposed• Headgear adjustable to cover forehead, ears,
cheeks, chin; Adjust for warmer weather or heavy tasks;
• Allow sweat to evaporate from the head - important in winter;
• A hood is helpful in cold, snowy, windy, or rainy weather:• Adjustable; • Big enough to fit over a helmet, • Protect the face from wind (at sides) and rain; • Good field of view, including sideways
• In extreme cold and wind – a balaclava or facemask is recommended.
REDUCING COLD INJURY RISK Protecting extremities: Head
• Consider dexterity and tactile sensitivity. • Gloves - slip-resistant palms and finger pads.
Additional grip force is otherwise applied to prevent object from slipping;
• Mittens – greater protection than gloves in very cold temperatures. Consider if dexterity not a major issue;
• Double gloving - thin inner glove (PES, PP, WO) under work gloves/mittens recommended if precision tasks must be carried out in the cold.
• Rough/injurious material e.g. logs, building materials, chemicals etc. – wear safety gloves.
• Replace Wet gloves with dry ones during work shift
REDUCING COLD INJURY RISK Protecting extremities: Hands
Foot cooling occurs esp. if standing still, & when footwear is damp or wet.Outerwear (e.g., boots, shoes):• Adequate traction for walking/climbing surfaces/conditions;Innerwear (socks, liners, and insoles) • Soles should be thick; • Loose insoles increase thermal insulation - can be removed and dried.• Keep footwear/feet dry; moisture reduces insulation, can cause sores. • Remove footwear during breaks to let footwear dry and feet “breathe,” if
possible. Change damp socks for dry ones; • Optimize Innerwear and outerwear are as a unified footwear system.
REDUCING COLD INJURY RISK Protecting extremities: Feet
REDUCING COLD RISKOccupational Health Care
• Older workers, people with medical problems at higher risk;• Alcohol, drugs – impaired judgment; hypothermia
associated;• Physical condition; • Seek warm shelter if:
• Heavy shivering, • Uncomfortable sensation of coldness, • Severe fatigue, drowsiness, or euphoria.
• Energy – warm, sweet, caffeine-free non-alcoloholic drinks, soup.
• Lotions to prevent chapped skin.
REDUCING COLD RISKInformation and training
Through training, employees take responsibility for cold management.
Training to include:• Identifying personal warning signs of over-exposure to cold;• Hazards of cold air, moisture, and contact with cold materials.• Protective clothing – especially for the extremities (hands, feet
and head)• Using PPE (e.g. safety helmets) with cold protective clothing• Train key personnel - update knowledge of cold related hazards• Train new workers on cold work risks.
REDUCING COLD RISKThermal (Insulating) Barriers
Reduce conductive heat loss: thermal mats on cold floors;
pipe insulation tubing or tape on cold skin-contact points.
REDUCING COLD RISKHeat Generation
Ready to use. 105°F
ProHeat reusable. 130º F
Toe Warmers. to 6 hrs.
Adhesive Insole Foot Warmer - 8+
Hours
REDUCING COLD RISKHeat Generation
Heat Factory Heated Back Wrap for use with Heat Factory Hand & Body Warmers
Venture Heated Glove Liner
Men’s Battery Heated Base Layer
Maradyne 503012 Volt Cab Heater 12,500 BTU. 7” square. Hose connectors.
Thank You!
QUESTIONS/COMMENTS?