1. GENERAL VENTILATION …examination of the use of “fresh air” to dilute contaminants to acceptable levels

2. Applications of General Ventilation zdilution of airborne contaminants to acceptable levels zcontrol fire/explosion risks zminimize odors or other nuisances zmaintain “comfort”

3. Natural Ventilation z always a factor via infiltration, etc. z design of natural ventilation via ypressure gradient yair density difference z equations/examples

4. Mechanical Ventilation zcreation of air flow by “artificial” means zusually required because infiltration is low volume & not controllable zgeneral ventilation vs local exhaust

5. General Ventilation May be OK IF... zair contaminants are of low toxicity zconcentrations are not high/hazardous zemission rate is fairly low & constant zcontaminant sources are dispersed zother solutions are less practical zuncontaminated “fresh air” is available

6. …and usually is NOT Ok if... zcontaminants are moderately toxic zconcentrations are high/hazardous zemissions vary with time, e.g. batch operation. zair must pass through breathing zone zre-entrainment of contaminant is likely zcontrol at source is more appropriate

7. DESIGN PRINCIPLES z determine amount of air required z locate exhaust near source z establish appropriate air flow pattern z replace exhausted air z avoid re-entry of exhausted air

8. HVAC Standards Affecting IAQ zASHRAE 62-1999: Ventilation for Acceptable Air Quality zASHRAE 55-1992: Thermal Environmental Conditions for Human Occupancy zASHRAE 52-1992: Methods of Testing Air Cleaning Devices Used in General Ventilation for Removing Particulate Matter zProposed OSHA IAQ Standard

9. OA Required for Specific Occupancies (ASHRAE 62-1999) ApplicationEstimated Max. Occupancy per 1,000 sq/ft cfm/person OA Commercial dry cleaners 30 Office space720 Smoking lounge7060 Conference room5020 Laboratories3020

10. Causes of IAQ Problems z Deficiencies in ventilation of the building z Indoor air contaminants z Outdoor sources z No identified cause

11. Equations zCalculating Dilution Air Volumes yFor health protection (where target concentration is PEL/TLV) xPure xMixtures If solvent produce similar (additive) effects, the total dilution air required must be determined by calculating volume for each solvent and summing If solvents do not produce similar effects, the largest volume calculated for individual components should be used If any doubt about additive effects, assume they are additive yFor fire and explosion protection (where target concentration is LEL) xDoes not apply where workers are exposed to vapors. In these cases, the dilution rates above for health protection should always be used xAir density adjustment

12. K Factor Some considerations that may be looked at in determining the K Factor: zThe mixing and distribution of replacement air zThe toxicity of the solvent zDuration of process zLocation of workers to sources zLocation and number of points of generation zChanges in ventilation systems

13. Role of IH? z Understand HVAC system components z Determine operating parameters z Perform ventilation checks