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Terms and Units
Terms and Units
radian = an angular measurement
term (rad)
A, B, and C = Boolean Variables
180° = number of degrees in one-half circle
π = the constant, pi (3.14159)
~
Used to describe the relationship between
radian, angular measurement and degrees.
(+) = the logic OR operator
(·) = the logic AND operator
~
Commutative laws for Boolean
Variables.
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Terms and Units
Terms and Units
P = present value ($)
A = annual investment or payment ($)
A = annual investment or payment ($)
P = present value ($)
I = interest rate (%)
I = interest rate (%)
n = number of years
~
Used to calculate the present value of
a series of equal annual amounts.
n = number of years
~
Used to calculate annual payments
based on a single present amount.
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Terms and Units
Terms and Units
A = annual investment or payment ($)
F = future value ($)
A = annual investment or
payment ($)
I = interest rate (%)
F = future value ($)
n = number of years
~
Used to calculate the annual
investment needed to obtain a future
amount.
I = interest rate (%)
n = number of years
~
Used to determine the future value of an investment
based on an annual investment.
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Terms and Units
Terms and Units
F = future value ($)
P = present value ($)
P = present value ($)
F = future value ($)
I = interest rate (%)
I = interest rate (%)
n = number of years
~
Used to calculate the future value of a
present amount of money.
n = number of years
~
Used to calculate the present value of
a future dollar amount.
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Terms and Units
Terms and Units
A = Boolean Variable
A, B, and C = Boolean Variables
A’ = Boolean inverse of A
(+) = the logic OR operator
(+) = the logic OR operator
(·) = the logic AND operator
~
Distributive laws for Boolean
Variables
(·) = the logic AND operator
~
Identity and inverse Boolean Variables
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Terms and Units
Terms and Units
LI = Lifting Index
a = coefficient of the x2 term
LW = Load Weight
b = coefficient of the x term
RWL = recommended weight limit
~
Used to estimate the level of
physical stress for a given lifting
task.
c = number in quadratic equation
(not a coefficient of any x term)
~
Solutions of the quadratic
equations.
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Terms and Units
Terms and Units
Patm = atmospheric pressure (mmHg)
ppm = parts per million (ppm)
106 = conversion factor to express answer in
ppm
Pv = vapor pressure of agent or contaminant
at a specified temperature (mmHg)
~
Used to calculate the saturation
concentration of a gas or vapor in air.
RWL = recommended weight limit
HM = horizontal multiplier
DM = distance multiplier
FM = frequency multiplier
LC = load constant
VM = vertical multiplier
AM = asymmetric multiplier
CM = coupling multiplier
~
Used to determine the recommended weight limit, or the load that
can be tolerated by a healthy worker, over a long period of time,
without causing injury to the worker’s lower back.
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Terms and Units
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Terms and Units
n = number of moles of gas or vapor (unit-less)
ppm = parts per million (ppm)
T = absolute gas temperature Rankine (R); Kelvin (K)
V1; V2 = gas or vapor volume under conditions 1 and 2
(1)
R = gas constant for air
(0.082 liters atmospheres/moles K)
P1; P2 = gas or vapor pressure under conditions 1 and 2
(mmHg)
~
Used to adjust the volume of gases following changes
in pressure and temperature.
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m.w. = molecular weight of contaminant
24.45 = molar volume of any gas or vapor
at NTP
mg/m3 = milligrams of contaminant per cubic
meter of air (mg/m3)
~
Used to convert parts per million to mg/m3.
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Terms and Units
Terms and Units
log = logarithm (base 10)
F1...n = weight % of chemical in liquid (unit-less
decimal)
[H+] = hydrogen ion (proton) concentration
in moles per liter (M)
pH = an indication of the acidity or alkalinity
of a liquid (0-14 unit-less)
~
Used to determine the pH of a given
solution.
TLV1...n = Threshold Limit Value of the
contaminant (mg/m3)
TLVmix = Threshold Limit Value of a mixture of
chemicals with additive effects (mg/m3)
~
Used to determine the TLV of a mixture.
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Terms and Units
Terms and Units
WBGT = Wet Bulb Globe Temperature
Index, °C
vapor/hazard ratio = relative risk indicator (unit-less)
WB = Wet Bulb Temperature, °C
exposure guideline = acceptable occupational
exposure limit
sat. concentration = the saturation (equilibrium)
vapor concentration of a gas or vapor (ppm)
~
Used to determine the inhalation hazard, by
determining the ratio of equilibrium concentration
relative to the allowable level.
GT = Globe Temperature, °C
~
Used to estimate heat stress on
workers without a solar load.
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Terms and Units
Terms and Units
M = metabolic heat (kcal/hr; BTU/hr)
W = external work rate (kcal/hr; BTU/hr)
WBGT = Wet Bulb Globe Temperature
Index, °C
E = evaporative heat loss (kcal/hr; BTU/hr)
WB = Wet Bulb Temperature, °C
ΔS = change in amount of heat stored by the body (kcal/hr; BTU/hr)
GT = Globe Temperature, °C
C = convective heat loss/gain from air movement (kcal/hr; BTU/hr)
R = radiant heat loss/gain from the flow of electromagnetic energy
(kcal/hr; BTU/hr)
~
Used to describe how a body maintains temperature equilibrium
throughout shifts in body heat content.
DB = Dry Bulb Temperature, °C
~
Used to estimate heat stress on workers
engaged in outdoor tasks, with sun
exposure.
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Terms and Units
95 = average skin temperature (°F)
tw = wall temperature; mean radiant
temperature of surroundings (°F)
R = radiant heat loss/gain from flow of
electromagnetic energy
(kcal/hr; BTU/hr)
~
Used to calculate radiant heat
gain/loss in body heat.
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Terms and Units
Tα = air temperature (°F)
v = air velocity (fpm)
C = convective heat loss/gain from air
movement (kcal/hr; BTU/hr)
~
Used to determine convective heat
gain/loss in body heat.
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Terms and Units
Terms and Units
cfm = cubic feet per minute of air (cfm)
2.4 = clothing-related constant
v = air velocity (fpm)
ΔT = change in temperature (°F)
1.08 = constant based on density and specific heat
of air
Total Sensible Heat = amount of heat energy that
changes only the temperature, and not the physical
state, of a substance (BTU/hr)
~
Used to calculate the volumetric flow rate required to
control sensible heat production.
vpw = vapor pressure of water (mmHg)
42 = water vapor pressure of the skin at 95°F
Emax = maximum evaporative heat loss possible
(kcal/hr; BTU/hr)
~
Used to calculate the maximum evaporative cooling
effect possible on a body performing work, taking
into account water vapor pressure and wind speed.
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Terms and Units
Terms and Units
tR = temperature in degrees Rankine (°R)
HIS = heat stress index (%)
tF = temperature in degrees Fahrenheit (°F)
100 = constant to express HSI in percent
460 = the conversion term for Fahrenheit
to Rankine
~
Used to convert between the Rankine and
Fahrenheit temperature scales.
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Emax = maximum evaporative heat loss possible
(kcal/hr; BTU/hr)
Ereq = amount of evaporative heat loss required to
avoid heat stress (kcal/hr; BTU/hr)
~
Used to calculate the heat stress index, based on
the relationship between required evaporative heat
loss and maximum evaporative heat loss.
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Terms and Units
tK = temperature in degrees Kelvin (K)
tc = temperature in degrees Celsius (°C)
273.15 = conversion term for Celcius
to Kelvin
~
Used to convert between the Kelvin and
Celsius temperature scales.
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