Work Climate

1
Work Climate Toxicology

• Indoor Air Quality
• Comfort
• Heat Stress
• Cold Stress

2
Indoor Air Quality (IAQ)

• Coinciding with energy insulation improvements,
  building air quality has degraded.
• IAQ sometimes exceeds Environmental Protection
  Agency (EPA) limits for OUTDOOR air quality!
• ACGIH(American Council of Governmental Industrial
  Hygienists) has established IAQ standards for
  industrial applications only. NO residential or
  commercial standards currently exist.

3
Symptoms of Air Quality Problems

• Periodic/chronic exposure
• Headaches, allergies, coughing
• Irritation of mucous membranes such as the nose,
  mouth, throat and lungs
• Tearing, redness, and irritation of the eyes
• Mood swings, fatigue, irritability
• Chronic exposure
• Damage to the liver, kidney, lungs, brain
• Cancer, death

4
Testing of IAQ

• Dangerous compounds, such as carbon monoxide or
  methane (without added odorant) cannot be
  detected w/o special equipment
• Some dangerous particulates, such as asbestos
  fibers, do not cause problems until 20 yrs after
  inhalation
• Certified Industrial Hygienists usu perform the
  IAQ tests or passive systems can be used

5
Ventilation

• ASHRAE (Amer. Society of Heating, Refrigeration,
  and Air-Conditioning Engrs) standards include
  air, odor, vent volume.
• Insufficient ventilation and tight buildings can
  lead to sick building syndrome interior
  pollutants are not dispersed (car exhaust,
  cigarette smoke, mites and fungi, etc.)
• Location of supply and return vents are important
  considerations

6
Air Volume and Quality

• Volume of air required is proportional to local
  contaminants.
• Carbon dioxide may be limiting.
• Body odors and cigarette smoke can be
  contaminants.
• For forced-air heating and cooling, ventilation
  volume may be determined by room temperature.

7
Shop Environments

• Local contaminants, such as dust and fumes may
  pollute the air.
• Solution strategies
• Decrease the concentration of the contaminant.
• Reduce worker exposure duration.
• Consider ventilation.

8
Area Ventilation

• Use when contaminant sources are diffuse.
• Keep the contaminant source downwind from the
  person.
• Locate the source as close to the exhaust as
  possible.

9
Local Ventilation

• Capture the contaminant directly.
• Dump exhaust air outdoors or filter it.
• Make filter systems fail-safe.
• For explosive substances, TLV (threshold limit
  value) is a concern.
• Consider reusing the air after filtration
  (usually done with office air).

10
Comfort

• Ultimate objective of any HVAC system is to
  maximize human thermal comfort.
• This comfort is maximized by establishing a heat
  balance between the occupant and his/her
  environment.
• The body can exchange heat via conduction,
  convection or radiation
• Air temperature, humidity, clothing, air motion
  and surface temp of surroundings all affect rate
  that a human body can dissipate heat

11
Ex For 80F (dry bulb) w/ 80 humidity Wet bulb
75F Dew pt 73F Enthalpy38
Comfort Zone
12
Psychrometric Charts

• Find the relative humidity, then find the dry
  bulb temperature that intersects

A
A Humidifying only B Heating and humidifying C
Sensible heating only D Chemical
dehumidifying E Dehumidifying only F Cooling
and dehumidifying G Sensible cooling only H
Evaporative cooling only
H
B
G
C
F
D
E
13
Compensating Factors

• Clothing
• Activity
• Air velocity
• Mean radiant temperature
• Time of exposure
• Time of Day, Season of year
• Gender Age of occupant

14
Individual Adjustment

• Conventional approach is to set conditions to
  match comfort zone.
• Desktop controls allow individuals to set their
  own conditions.
• Occupancy sensors turn off equipment, lights,
  fans.
• Energy savings may be substantial.

15
Heat Stress

• Heat effects measured officially by body core
  temperature
• Core temps over 38C can cause damage such as
  infertility, birth defects in pregnant womens
  fetuses
• Work performance decreases as heat peaks,
  although motivation can overcome this effect
• Illnesses include heat stroke (most severe), heat
  exhaustion, heat cramps, and heat disorders, such
  as rashes, dehydration

16
Reduction of Heat Stress

• Homeostasis the body automatically
  thermoregulates itself.
• The hypothalmus compares this with the bodys
  setpoint.
• The difference can cause sweating, shivering,
  blood vessel vasodilation
• Work, metabolism, clothing can affect

17
Reduction of Heat Stress

• Consider human body heat storage.
• Reduce metabolic rate (by mechanization, working
  slower).
• Consider work being done.
• Reduce radiant load (work in the shade, use heat
  shielding, or wear long sleeves).
• Maximize convective heat loss (more air).
• Increase evaporative heat transfer (less humid).
• Consider conductive cooling (such as ice vests).

18
Cold Stress

• Extreme cold gives loss of mental performance and
  decreased manual dexterity.
• Wind Chill Index gives us a combined effect
  measurement of air velocity, temp
• Clothing, or avoidance are the primary defense
  against cold stress
• Vigilance decreases when the core temperature
  drops

19
Protection Against Cold Stress

• Layer clothing.
• Shoes should accommodate two pairs of socks.
• Keep clothing dry.
• Protect the head.
• Warm the hands by wearing a jacket.
• For exercise, use breathable fabrics.
• Reduce air velocity.

20
Other Factors in Cold Stress

• Cover vents or use diffusers or deflectors.
• Keep floor temperature at 73.5º in offices.
• Avoid contact with cold metal.
• Drink fluids to prevent dehydration.
• Avoid caffeine (a vasodilator).

21
Toxicology

• Deals with the long-term effects of foreign
  chemicals upon the body
• Depend on type and amount, can be either critical
  or cumulative (like CTDs)
• May be a long lag between exposure and response
  (e.g., asbestos)

22
Poisons

• Effects often tested on animals ?
• Threshold Limit Values (TLVs) help determine
  whether effects are reversible or not
• TLVs are directly proportional to body mass,
  target organ susceptibility

23
Threshold Limit Values

• Issued by American Conference of Governmental
  Industrial Hygienists.
• Three different types
• Time-weighted average (TLV-TWA) recognizes
  chronic effects
• Short-term exposure limit (TLV-STEL) concerned
  with acute effects
• Ceiling (TLV-C) an absolute limit of
  concentration

24
Poison Delivery Routes

• Skin Natural barrier is compromised with open
  cuts/abrasions
• Mouth Forbid eating/drinking/smoking in a work
  area to avoid ingestion
• Lungs Particle size determines what is inhaled,
  retained. Small particles are more dangerous
  (lt10 mm).

25
Toxicology Controls

• Can be via engineering, administrative or
  personal protection methods

Table 26.2
26
Personal Protection

• Least desirable approach consider engineering or
  administrative controls instead!
• Should be professionally fitted
• May involve completely sealed bodysuit and hood,
  or just a face mask and gloves
• May need SCBA (self-contained breathing
  apparatus) training
• Beards and face masks dont mix
• Verbal communication is extremely difficult
• Need to shower isolate clothing after removal