Page 66 - Industrial Ventilation Design Guidebook

3.9 LOCAL PROTECTION 3 I

Step 2: Conditions in Local Zone
Calculate the conditions in the local zone.

Step 3: Comparison to Target Levels of Local Zone
Compare calculated conditions to the target levels of the zone.

Step 4: Process Methods
Consider whether there are any process methods to reduce loads.

Step 5: Ventilation Methods
Select the optimal ventilation method to reduce emissions and/or to pro-
tect workers, (For details, see the subtree Fig. 3.10.)

Step 6: Effect of Local Protection on the Emission of the Process
Consider whether the local protection influences the emission of the pro-
cess. In that case, return to Calculation of Local Loads.

Step 7; Respiratory Protective Equipment
If no other method provides protection to the worker, design respiratory
protective equipment. In the design phase, the minimum is to identify the need
for personal protection.
The tools for this task include:
• Balances {heat, contaminants, etc.)
• Computational fluid dynamics (CFD)
• Empirical methods
« Process methods
• Ventilation methods (see the subtree in Fig. 3.10.)

Explanations of Fig. 3.10

Step /: Source Characteristics
Characteristics are defined in Source Description.

Step 2: Alternative Prevention Methods
Select methods that could be used in this case.
Step 3; Calculation of Prevention Methods
Calculate performances of different methods and make them comparable.

Step 4: Selection of the Hood
• Select the method that is optimal in this case (efficiency, economy,
etc.).
• After selection, return to Local Protection (design of general ventilation
system).
Step 5; Design of Conveying System
Design conveying system to convey captured contaminants away (sepa-
rate tree).