Occupational Heat Stress

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Occupational Heat Stress
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Course Outline

• Heat Stress Defined
• Contributors to Heat Stress
• The Bodies Response
• Monitoring for Heat Stress
• Heat Stress Controls
• The Management of Heat Stress

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Sources of Information

• ACGIH
• OSHA
• NIOSH
• Electrical Power Research Institute
• National Weather Service
• Experienced Employers
• World Health Organization

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Possible Approaches

• WBGT
• Core Temperature
• Sweat Rates
• Urine Sodium Levels
• Recovery Heart Rate

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Where the heat comes from

• We generate some by our metabolism by converting
  our food to energy and using it to do work
• Some may be added by the environment
• Some may be taken away by the environment
• Clothing can trap the heat

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Loss ofthermoregulation balance
Heat In
Heat Out
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Heat Stress Definition

• Net Heat Load on the Body from the Combined
  Contributions of Metabolic Heat Production and
  External Environmental Factors.

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Heat Strain

• The Net Physiological Load Resulting from Heat
  Stress

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Heat Index

• Combines temperature relative humidity for a
  feels like value

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Relative Humidity

• Ratio of amount of water vapor in air compared to
  greatest amount possible at a specific
  temperature
• Absolute humidity relates to amount of water
  vapor in the air

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Typical Industries with Heat Stress Potential

• Iron Steel Foundries
• Brick Firing Ceramics
• Construction
• Glass Products
• Rubber Products
• Utilities
• Bakeries
• Military

• Canneries
• Mining
• Chemical Processing
• Smelters
• Steam Turners
• Laundries
• Fire Fighting
• Haz-Mat Applications
• Sports

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Industrial Hygiene Model

• Identify
• Monitor
• Control
• Eliminate
• Minimize
• Protect
• PPE
• Training

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Environmental Factors

• Temperature
• Evaporative Potential
• Air Movement
• Radiant Factor

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Our Body Responds

• Hypothalamus-the bodys temperature control
  center
• Perspiration
• Blood Flow

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Evaporation defined

• Process by which water turns to vapor without
  reaching its boiling point
• Molecules leave the surface taking energy with
  them thus cooling

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When the responses fail, reactions occur

• Rash
• Cramping
• Exhaustion
• Syncope (fainting)
• Stroke
• Death

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Exhaustion

• Prolonged sweatingIllness induced dehydration
• Thirst Weakness Headache Dizziness Uncoordinate
  d
• Cool downRe-hydrate

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Syncope

• Prolonged positionPooling of blood
• Blurred visionFainting
• Lay downRe-hydrate

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Stroke

• Extreme exposureOut of conditionAdditional
  Contributors
• ChillsConvulsionsUnconscious
• Immediate coolingMedical care

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Prolonged exposures

• Every physical symptomyou can imagine

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Key Body Temperatures

• 37oC 98.6oF Normal
• 38oC 100.4oF Long exposure
• 38.5oC 101.3oF
• 39oC 102.2oF Short exposure
• 41oC 105.8oF Life threatening

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Conversion Formulas

• Centigrade to FahrenheitC (F-32) x 5/9

• Fahrenheit to CentigradeF 9/5 C 32

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Metabolism defined

• The rate of converting food to useable energy and
  heat within the body

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Classification of Activities
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Heat Stress Symptoms

• Sweat cessation
• Skin color change
• Shivering
• Irritability
• Disorientation

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Internal Factors

• Fluid balance
• Metabolism
• Perspiration ability

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Complicating Factors

• Age
• Health
• Medication
• Acclimatization/conditioning

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Assessments Guaranteedto Fail

• Thirst
• Self appraisal the double edged sword

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Self Regulation

• Worker knows self better than anyone or
  anything - vs.
• Pay incentives
• Macho Phenomenon
• Emergencies
• Labor/Management Relationship

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Heat Stress Consequences

• Fatigue, tired feeling
• Reduced productivity
• Increased errors, accidents----------------------
  ---------------------------
• Risk of heat related disorders

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This suggests two areas for assessment

• ExternalEvaluate the ambient environment and
  its affects on the person

• InternalEvaluate the heat being generated
  within the person and/or its individual
  physiological affects

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Wet Bulb Globe Temperature

• Wet Sensor assesses evaporation (humidity air
  movement)-as distilled water evaporates from
  cup, it cools the sensor
• Globe Sensor assesses radiant component
• Bulb Sensor assesses ambient temperature

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WBGT Heat Stress Index

• Outdoors with Solar Load0.7 NWB 0.2 GT 0.1
  DB
• Indoors or Outdoors without Solar Load0.7 NWB
  0.3 GT
• See Latest ACGIH TLV Guide for assessment of work
  rate and clothing

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Evaluation and Control

• Classify Type of Work Load
• Light
• Moderate
• Heavy
• Correction Factors for Type of Work
• WBGT is Measured and Rest Time is Determined

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Examples of Permissible Heat Exposure Threshold
Limit Values
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WBGT Correction Factors for Clothing (in C)
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Other Heat Stress Issues

• Standards Developed for
• Acclimatized, Hydrated, Unmedicated, Healthy
  Workers, Wearing Light-weight Summer Clothing
• ISO Standards Suggests 3 Point Monitoring in
  Certain Environments
• Current Standards State Workers Should not Work
  if Deep Body Temp Exceeds 38C

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QUESTEMP 10 Non-Datalogging Area Monitor

• Wet Bulb, Dry Bulb Globe Temps
• Indoor Outdoor WBGT Indices
• Celcius and Farenheit Scales
• Remote Sensor Capable (100 ft.)
• 9V Alkaline or AC (Optional Adapter)

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QUESTEMP 15 DataloggingArea Monitor

• Same As QUESTEMP 10 PLUS
• Time History Datalogging
• Real-time Clock w/ Programmable Start-Stop
• Optionally Supports (3) Sensor Arrays
• Custom WBGT Programmable
• Temperature-Actuated Alarm Output
• Outputs to Serial/Parallel Printers PC

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QUESTEMP 30 Non-Datalogging Area Monitor

• Replacement for QUESTEMP 10
• Larger, Covered WB Reservoir
• Shielded DB Sensor
• Multi-Lingual
• 200 ft Remote Sensor Capable
• ETL, cETL, DEMKO, CE

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QUESTEMP 32 Non-Datalogging Area Monitor

• Same as QUESTEMP 30, PLUS
• On-Board RH Sensor for Heat Index

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Sensors Care

• Remote
• Multiple Input ISO
• Calibration

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Sensor Range Accuracy

• Range - 5 to 50o C 23 to 122o F
• Accuracy /- 0.5o C

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Settling Time

• Needs to be in environment for 30 minutes

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Calculation Example

• Control Rod Drive in a dry well
• Light work rate
• Coveralls with a plastic protective suit
• Dry bulb 91oWet bulb 71oGlobe 91o
• WBGT ???

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Calculation Example

• Feed water check valve in steam valve
• Moderate work
• Coveralls with plastic protective suit
• Dry bulb 114Wet bulb 84Globe 118
• WBGT ???

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Calculation Example

• Turbine repair on low pressure side
• Moderate work
• Coveralls with plastic protective suit
• Dry bulb 109Wet bulb 94Globe 106
• WBGT ???

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Calculating Average from Multiple Exposures

• WBGT1 x t1 WBGT2 x t2WBGTn x tn t1 t2
  tn

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Calculating Average from Multiple Exposures

• WBGT of 88 for 2 hours
• WBGT of 92 for 1 hour
• WBGT of 101 for 1 hour
• Equivalent WBGT ???

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New Proposed Standards

• Temperatures for Unacclimatized Workers
• Slightly Higher Temps. For Acclimatized
• WBGT Would be Screening Tool
• Personal Monitoring Would be Needed
• Among other Options Limit Deep Body Temperature
  to 38 C for Unacclimatized and 38.5 for
  Acclimatized

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Proposed Decision Tree
No
Yes
Yes
No
Yes
No
No
Yes
Yes
No
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Personal Monitoring

• Key is to identify heat stress as it begins
• Personal monitoring goes beyond ambient measures
  by considering affects of-medications -alcohol
  -diseases -micro environments-individual
  acclimatization

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Personal Monitoring

• Core Temperature- rectal, oral, esophageal
• Skin surface and heart rate
• Auditory Canal

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Personal Heat StressMonitor

• Questemp II
• Monitors body temperature in the ear
• Evaluates worker response rather than ambient
  potential
• Micro environments

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hs-3800 DataloggingPersonal Monitor

• Displays Logs
• Body Temp
• Heart Rate
• Built-in EPRI Tables
• Real-time Clock
• Pre-set Warn Action Alarms
• Outputs to Serial Printer PC

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Program Evaluation

• Workplace description
• Work activity
• Equipment
• History
• Exposure characteristics

• Weather influence
• Controls in Place
• Training
• Liquids
• Time/conditioning mgmt
• Monitoring
• 1st Aid
• Medical Screening

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Managing the exposure

• Re-hydration
• Ventilation
• Humidity Reduction
• Rest/Work Scheduling
• Change Process or Procedure
• Clothing
• Cooling Vests

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Example of a cooling vest
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Education Training

• Elements of Heat Stress
• Human Factors
• Managing Your Own Exposure
• Controls in Place