Indoor Air Quality

1. Indoor Air Quality Industrial Hygiene IENG 341 Carter J. Kerk Industrial Engineering Program SD Tech Spring 2006

2. Assignments • Read Nims, Chapter 6 • Do the Critical Thinking Questions on p. 168

3. Outline • Introduction • Indoor air quality as a public health concern • Heating, ventilating, and air conditioning systems (HVAC) • Basic instruments for use in IAQ studies • Microorganism contamination and IAQ • Radon and asbestos

4. Introduction • Indoor Air Quality (IAQ) • Recent phenomenon • Due to construction of energy conservation construction techniques starting in the 1970s • Sick Building Syndrome • Tight Building Syndrome • Gases emitted from cleaning chemicals, building materials, office furniture, carpets • Radon, asbestos, Legionella (put Rapid on the national map!) • Industrial and Non-Industrial (e.g., schools) • Ventilation Issues

5. Indoor Air Quality as a Public Health Concern • The energy crisis in the 1970s spawned construction of thousands of energy efficient buildings • Sealed windows • Thermostats not accessible or adjustable by occupants • Self-contained environments with controls for temperature, humidity, airflow • Complaints: odors, too hot, too cold • Physical symptoms: headaches, respiratory irritation

6. Temperature • Too hot, too cold, too drafty • Conditions vary with seasonal changes and HVAC operation

7. Humidity • Air is too dry • Contributing to irritation of the respiratory tract and eyes • Too much humidity • Contributes to growth of microorganisms, encourages odors and mustiness

8. Stuffiness or Lack of Circulation • Can be related to location of diffusers or outlets relative to occupants • HVAC system is undersized, poorly maintained, or improperly operated • Poor circulation can lead to stratification of air • Some areas benefit, other areas suffer • Dead zones may allow odors and CO2 to accumulate to unacceptable levels

9. Odors • Many objectionable odors: coffee, body odor, vehicle exhaust, chemical smells • New construction or renovation odors: fresh paint, off gassing from furniture or carpet fabric (formaldehyde) • Odors may be drawn in from outside • Air intakes located near loading docks, trash dumpsters, incinerators, exhaust stacks

10. Physical Symptoms • Dryness of eyes and respiratory tract, headaches, tiredness, upset stomach, runny nose, nasal congestion, drowsiness • CO2 levels > 1000 ppm may cause headaches and drowsiness • Symptoms are often non-specific enough to draw a cause-effect relationship

11. What is an OLF? • Created in Denmark to measure the bioeffluent odor load produced by a “standard” building occupant • Person who bathes 0.7 times/day • Changes their underwear daily • Has skin surface of 1.8 m2 • Spends their day in sedentary or seated tasks • Example: a wet and moldy AC filter might produce an undesirable odor at a level equivalent to 10 olfs

12. US Statistics on IAQ • About half of IAQ problems were attributed to the HVAC system • Poor system design • Poor maintenance • About 40% due to chemical contaminants or microbes • In 10% of the cases, no cause could be found

13. Psychosocial Factors • Do not disregard this category • Job satisfaction, degree of control over one’s environment, window placement and window control • Read the two case studies in Box 6-1

14. OSHA Standards for IAQ • On December 17, 2001, OSHA withdrew its IAQ proposal and terminated rulemaking proceedings • Proposed • CO2 < 800 ppm • RH < 60% • Maintain HVAC records on original design specifications, cleaning, repairs • Exhausting designated smoking area to the outside and keeping them under negative pressure • Locating air intakes of systems to prevent capturing outside air contaminants

15. ASHRAE • American Society of Heating, Refrigerating, and Air-Conditioning Engineers • www.ashrae.org • 62-1989, Ventilation for Acceptable Air Quality • 55-1992, Thermal Environmental Conditions for Human Occupancy • 52-1992, Methods of Testing Air Cleaning Devices Used in General Ventilation for Removing Particulate Matter

16. HVAC Systems • HVAC – Heating, Ventilating, and Air Conditioning Systems • Types • Single zone, constant volume • Single zone, variable volume • Multiple zone, constant volume • Multiple zone, variable volume • Hybrids

22. Checklist for HVAC Inspection • See Appendix 4

23. Fresh Air Recommendations • ASHRAE Recommendations • 1905 – 30 cfm / person • 1936 – 10 cfm / person • 1973 – 5 cfm / person • Energy crisis concerns • 1989 – 20 cfm / person • Concerns about 2nd hand smoke

24. Basic Instruments for IAQ Studies • Thermometer • Velometer (air velocity) • Rotating vane anemometer • Heated-wire anemometer • Gas Detection Instruments • Detector tubes • Psychrometer (relative humidity) • Smoke tubes • IAQ multi-function instruments • Air temperature, humidity, CO2, air velocity, dewpoint, computer interface

25. Volumetric Flow Rate, Q • Q = VA • Q, volumetric flow rate in cfm • V, velocity of air, fpm • A, area of the duct, ft2 • Example: Velometer reads 18 fpm at outlet face. Outlet measures 1.5’ by 2’. Find Q. • Q=VA=(18fpm)(1.5ft)(2ft)=(18fpm)(3ft2) • Q=54 cfm

26. Estimating Volumetric Flow Rate of Outside Air Using CO2 Concentration • QOA = (13,000 x) / (Cin – Cout) • QOA, volumetric flow rate of outside air, cfm • Cin, CO2 concentration inside, ppm • Cout, CO2 concentration outside, ppm • x, number of occupants • Example: Cout = 200 ppm, Cin = 800 ppm, x = 40 occupants • QOA = ((13000)(40))/(800-200)=867 cfm • 867 cfm per 40 occupants = 21.7 cfm/person • Compare to ASHRAE 1989 recommendation of 20 cfm/person

27. Estimate % Outside Air Using Temperature Information • %OA = (TRA – TSA)/(TRA – TOA) x 100% • OA, outside air • RA, return air • SA, supplied air • Example: TRA = 73F, TSA = 69F, TOA = 26F. Find %OA. • %OA = (73-69)/(73-26) x 100% • %OA = (4/47) x 100% = 8.5% • If you know Q and number of occupants, then you can calculate the cfm/person of fresh air from this percentage and compare to ASHRAE recommendation