Geoscience Reference
In-Depth Information
where
L
1
= Sound pressure level (dB).
I
= Sound intensity (W/m
2
).
I
o
= Reference sound intensity (W/m
2
).
15.7.5.17 Noise Reduction by Absorption
The amount of noise absorption from room surfaces is measured in sabins.
Noise reduction (dB) = 10 log
10
(
A
2
/
A
1
)
where
A
2
= Total amount of absorption in room after treatment (sabins).
A
1
= Total amount of absorption in room before treatment (sabins).
15.8 THERMAL STRESS
Appropriately controlling the temperature, humidity, and air distribution in work areas is an impor-
tant part of providing a safe and healthy workplace. A work environment in which the tempera-
ture is not properly controlled can be uncomfortable. Extremes of either heat or cold can be more
than uncomfortable—they can be dangerous. Operations involving high air temperatures, radiant
heat sources, high humidity, direct physical contact with hot objects, or strenuous physical activi-
ties have a high potential for inducing heat stress in employees engaged in such operations. Such
places include: iron and steel foundries, nonferrous foundries, brick-firing and ceramic plants, glass
products facilities, rubber products factories, electrical utilities (particularly boiler rooms), baker-
ies, confectioneries, commercial kitchens, laundries, food canneries, chemical plants, mining sites,
smelters, and steam tunnels (Spellman and Whiting, 2005). Outdoor activities conducted in hot
weather, such as construction, refining, asbestos abatement, and hazardous waste site activities,
especially those that require workers to wear semipermeable or impermeable protective clothing,
are also likely to cause heat stress among exposed workers.
15.8.1 C
ausal
F
aCtors
The occurrence of thermal stress to workers in the workplace can be attributed to various causal
factors as pointed out below.
• Age, weight, degree of physical itness, degree of acclimatization, metabolism, use of alco-
hol or drugs, and a variety of medical conditions such as hypertension all affect a person's
sensitivity to heat. However, even the type of clothing worn must be considered. Prior heat
injury predisposes an individual to additional injury.
• It is dificult to predict just who will be affected and when, because individual susceptibility
varies. In addition, environmental factors include more than the ambient air temperature.
Radiant heat, air movement, conduction, and relative humidity all affect an individual's
response to heat.
Heat stress and cold stress are major concerns of modern health and environmental professionals.
This section provides the information they need to know in order to overcome the hazards associ-
ated with extreme temperatures.
15.8.2 t
Thermal
C
omFort
Thermal comfort in the workplace is a function of a number of different factors. Temperature,
humidity, air distribution, personal preference, and acclimatization are all determinants of comfort
in the workplace. Determining optimum conditions, however, is not a simple process. To fully
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