**1.** General dilution ventilation equation:

Rate of accumulation = Rate of generation - Rate of removal

*Or*

VdC = Gdt - Q'Cdt

Where:

V is the volume of the room

G is the rate of generation

Q' is the effective volumetric flow rate

C is the concentration of gas or vapor

T is the time

At a constant concentration C and uniform generation rate, G

G(t_{2} -t_{1}) = Q' C(t_{2} -t_{1})

Q' =
(G/C)
*Equation 1*

Due to complete mixing, a constant value K is introduced thus making the equation

Q' = (Q/K)

This makes ** equation 1** as

Q = (G/C)* K

**2.** G = (Conv*SG*ER)/MW

Where:

G is the rate of generation

Conv is the volume in ft^{3} that 1 pt of liquid when vaporized, will occupy at
STP

SG is the specific gravity of the volatile liquid

ER is the evaporation rate of liquid, pts/min

MW is the molecular weight of the liquid.

So, Q' in ** equation 1** becomes

Q' = (403*10^{6}*SG*ER)/(MW*C)

**3.** C_{1}/TLV_{1} + C_{2}/TLV_{2} + C_{3}/TLV_{3}
+ C_{4}/TLV_{4} + …………..+ C_{5}/TLV_{5}

is the equation when two or more hazardous substances are present.

TLV is the threshold limit value

C is the concentration of the hazardous substance.

**4.** The basic heat balance equation is

DS = (M-W)± C ± R - E

Where:

DS is change in body heat content

(M-W) is the total metabolism - the external work performed

C is the convective heat exchange

R is the radiative heat exchange

E is the evaporative heat loss.

** Convection**

C = 0.65 V_{a}^{0.6} (t_{a}-t_{sk})

Where:

C is the convective heat exchange

V_{a} is the air velocity

t_{a }is the air temperature, ^{o}F

t_{sk} is the mean weighted skin temperature, usually assumed
to be 95 ^{o}F

** Radiation**

R = 15.0(t_{w} - t_{sk})

Where :

R is the radiative heat exchange

t_{w }is the mean radiant temperature, ^{o}F

t_{sk} is the mean weighted skin temperature,
usually assumed to be 95 ^{o}F

** Evaporation**

E = 2.4V_{a}^{0.6}(r_{sk}-r _{a})

Where:

E is the evaporative heat loss

V_{a} is the air velocity

r_{a} is
the water vapor pressure of ambient air, mm Hg

r_{sk }is
the water vapor of the skin assumed to be 42 mm Hg at 95 ^{o}F

**5.** WBGT **(indoor)** = 0.7t_{nwb} + 0.3t_{g}

Where:

t_{nwb} is the natural wet bulb temperature

t_{g} is the radiant or globe temperature

**6.** WBGT **(outdoor)** = 0.7t_{nwb} + 0.2t_{g} + t_{a}

Where:

t_{nwb} is the natural wet bulb temperature

t_{g} is the radiant or globe temperature

t_{a} is the ambient air temperature

7. Sensible Heat Rise can be determined by the formula

H_{s} = Q_{s }*_{ }
ρ * c_{p * }
ΔT * (60 min/hr)

Where

H_{s} = Sensible heat gain, BTU/hr

Q_{s }= Volumetric flow for sensible heat, cfm

_{ }ρ = Density of the
air, lbm/ft^{3}

c_{p } = Specific heat of the air, BTU/lbm-deg F

ΔT = Change in temperature, deg F

For air c_{p } = 0.24 BTU/lbm-deg F and _{ }ρ
= 0.075 lbm/ft^{3};

Then the equation becomes

H_{s} = 1.08 * Q_{s} *
ΔT

Go to Dilution ventilation.