Purpose of Ventilation: Ventilation systems are used to maintain adequate oxygen supply, control hazardous chemical concentrations, remove odors, control temperature and humidity, and remove contaminants at their source before they enter the workplace.
Types of Ventilation:
General Ventilation: Provides comfort and includes systems like air conditioning and heating.
Dilution Ventilation: Mixes fresh air with contaminated air to dilute contaminants, suitable for moderate toxicity and dispersed sources.
Local (Exhaust) Ventilation: Controls contaminants at their source before they mix with breathing air, ideal for highly toxic substances and single-source emissions.
Ventilation Equations and Calculations:
Volumetric Air Flow: Q=VAQ = VAQ=VA, where QQQ is volumetric flow rate (cfm), VVV is air velocity (fpm), and AAA is cross-sectional area (sq. ft.).
Static Pressure, Velocity Pressure, Total Pressure: TP=SP+VPTP = SP + VPTP=SP+VP, where TPTPTP is total pressure, SPSPSP is static pressure, and VPVPVP is velocity pressure.
Capture Velocity: Determines the minimum air velocity at a hood opening to capture contaminants effectively.
Examples and Applications:
Calculating contaminant concentration buildup over time.
Determining air changes per hour in a room.
Calculating hood entry losses and static pressures in ventilation systems.
Use of specific equations like those for calculating room air changes, capture velocities, and concentrations of contaminants.
Ventilation System Components:
Hoods: Designed to capture contaminants.
Ducts: Transport contaminated air to air-cleaning devices or stacks.
Fans: Generate airflow against system resistance.
Air-Cleaning Devices: Filter contaminants from the air.
Safety Considerations: Proper ventilation design is critical to maintaining safe working environments, controlling exposure levels to contaminants, and complying with health and safety regulations.
This summary captures the essential information provided in the text regarding ventilation systems and their applications in occupational safety and health contexts.
