Page 66 - 6848

affected. The result is that the system will plug more rapidly and the airflows at the
other hoods may not be adequate enough to remove contaminants.

What should you know about make-up air?

An important and sometimes overlooked aspect of local ventilation is the need
to provide enough air to replace the air that is exhausted from the workplace. If
enough make-up air is not provided when large volumes of air are exhausted, the
workplace becomes "starved" for air and negative pressure is created.
Negative pressure in the workplace increases resistance on the ventilation
system causing it to move less air. Air will also enter a building through cracks
around doors or windows or other small openings to try to "equal" the rate of air
being removed. The result is that workers may be exposed to cold air in the winter,
and additional heating costs may occur. One simple way to judge if a building is
under excessive negative pressure is if you have difficulty opening a door that pushed
into the room or building (the air wants to force the door closed).
A separate intake fan, located away from the exhaust fans, should be used to
bring in fresh, uncontaminated air from outside. This air must be clean and heated in
winter or cooled in summer, as needed.

8.3 Calculation of the Required Volumetric Flow Rate of Air in

the Ventilation Systems in Industrial Areas

According to the sanitary standards, all production and support facilities should
have ventilation

The amount of air that must be exhausted or makeup is calculated for several
factors, depending on the specific conditions of each building:

1) Calculation by the factor "people".

In normal indoor environment and lack of harmful substances or their content
3
in the normal volumetric flow rate L (m / h) is determined by the formula:

3
L  N  L ,  m / h

where N - number of employees;

L '- volumetric flow rate per 1 employee, taken depending on the specific
volume of the space VN, which accounts for each employee

3
VN = V / N, m /1 person

where V - the volume of the room,

3
If the specific volume VN is 20 m , volumetric flow rate the per 1 employee
should be submitted at least 30 m /h air;
3

4