Presentation Transcript

1. Indoor Air Quality Case Studies

   Kevin Renton
2. IAQ Intro – why this stressor is important The problem i.e. Health effect Legislation / Directives – incl. OEL, what guides us / restricts us How measured How controlled Challenges How practical/applicable to measure/assess Wrap up
3. Bad Parenting ???? or …….
4. Occupational Health Risk Assessment What to do? eyes, nose, and throat irritation, headaches, dizziness & fatigue
5. Table 1: Acceptable Indoor Air Quality – ASHRAE Good practice guidelines suggest an air velocity of at least 0.1m/s. The National Building Regulations, SANS 10400-1990, also requires that, in order to prevent the perception of draughts, the air velocity of air in an occupied room should not exceed 0.5m/s.
6. GUIDELINES USED
7. Case Studies: Sixty Practical Applications of OH&S Control Principles (Elemental industrial hygiene series) Dr. Jeff Burton
8. Are these complaints suggestive of a biological contamination of some sort? What complaint rate is suggestive of a real IAQ problem?
9. The IH took note of the odour complaints – most were suspiciously similar to complaints associated with microbiological problems. After conducting a survey, the IH determined that 33% o0f people were complaining. This was high – typically less than a few percentage of people would have such complaints. Complaints had begun in May, as warm weather hit the region.
10. What potential sources would the IH investigate (and eliminate)?
11. The IH was able to discount some possible odour sources right away – there had been no flooding or water damage episodes, no construction or remodelling was going on, no equipment was malfunctioning, there were no open chemical processes in the building and smoking had been outlawed several years ago.
12. What would be likely source of these complaints, given that complaints were isolated to two floors and complaints began at the beginning of summer?
13. Because no obvious source was quickly identified, the IH next turned to the air handling unit (AHU) and found that a dedicated AHU on the roof served both the 9th and 10th floors.
14. The IH routinely checked air flows at the supply and return registers in each office, with the following results: Air turnover rates seemed adequate, about 7 air changes/hour Outdoor air was being provided at about 10% of total supply, (typical of operations during the hot, humid summer months)
15. Indoor air temperatures and humidities were at the upper end of normal: 23- 24 deg C 55-65% relative humidity Indoor carbon dioxide samples were not abnormally high – av 900ppm Outdoor air concentrations of carbon dioxide av 370ppm
16. The IH also inspected the rooftop AHU equipment with the following results: All ductwork and connected controls were attached and operating properly The air filter system consisted of a roll type prefilter (MERV=5) and a bank of 2’x2’ pleated paper filters (MERV=10)
17. The roll filter had become defective during the winter and the filter removed until repairs could be made The 2’x2’ filter bank had 3 pleated filters missing and air was flowing unfiltered into the AHU through holes
18. IAQ Complaints in an Older Office Building
19. Occupants along the west wall of an office building complained of "odors, dust, smoke, cold air, and noise." Several had asked to be transferred to other areas. An Occupational Hygienist investigated.
20. Figure 1. Plan View of Office Building Area of Complaints Showing Locations of Thermostats (T), and Air Handler No.1 (AR1) on the Roof; North is Up
21. The space characterization data gathered by the IH included: The office space consists of offices along the outside walls of the single story building. .A large package-unit AHU was located on the roof; the system was a reheat type unit with supply and return ducts. The floor area was 5,000 square feet. A total of 35 people work in the office area.
22. The IH's walkthrough and investigation data included: . The office building was divided into four zones; air was supplied to each office space from supply registers in the ceiling and returned at ceiling grilles. . Thermostats were located in four locations in the hallways. Each was locked and only the HV AC operator had the key. Temperatures were set by "consensus."
23. . Average indoor measured dry bulb temperature = 23° C; range = 20 -24°C; RH = 30-50%. The total amount of air, Q, being delivered to the space was QSA = 2,500 cfm; percent OA 30%; the amount of air being returned to the AHU, QRA = 3,000 cfm. 70 792 litre/min 33 l/s person
24. Using indicator tubes, CO = 0 ppm and CO2 = 900 ppm. Other: Odours and dust were observed in offices along the west wall. Water had infiltrated the roof of the building during a severe storm two months ago. Outside: Stormy; west winds at 10 mph, outside temperature, 40°F, RH, near 100%. A new building was being constructed on the west side of the building. Building construction: Concrete block; aluminium windows; 25 years old.
25. . . The building was quiet dusty; housekeeping was performed weekly during the evenings. . The AHU had no provision for humidifying the air.
26. Please evaluate the above data and write your- responses to the following questions 1.Was there a genuine IAQ problem? 2. Were the following IAQ-related parameters okay/not okay? Air distribution? Total air volume flowrates? OA delivery?
27. Carbon Dioxide Concen trations? Thermal Comfort conditions? Air contaminants? Air contaminant concentrations? HV AC problems?
28. What do think may be the sources and/or causes of the complaints?
29. List possible contributing factors.
30. List possible corrective actions or controls.
31. Outcome. These were the findings and recommendations for control: . Temperatures, RHs, CO, CO2, QOA, thermostat locations, supply and return registers-all appeared within normal and acceptable criteria. Dust, odors, temperature extremes, and noise suggested a genuine IAQ problem. QRA = 3,000 cfmand QSA =2500 cfm . The building was under negative pressure because more air was being returned to the AHU than being supplied to the building. (Should be positive.) . Air was infiltrating the building along the walls, especially the west wall because the wind was from the west. . Construction dust, odours, noise, and cold air were infiltrating the west wall.
32. Recommendations for control: -- Rebalance the HV AC system to bring the building into a slight positive pressure (re: the outside). -- Maintain tight control of remodeling /renovation activities in the future.
33. Medical Laboratory
34. The air velocity measurements did not comply with the minimum standard of at least 0.1m/s in approximately half of the areas that were evaluated. The maximum air velocity of 0.5m/s was not exceeded in any of the rooms.
35. Recommendations “Once the modifications have been implemented, employees should be trained how to maintain the proposed temperature adjustment” Involve the Engineer in the H&S Committee – Team approach Including MANAGEMENT. Changing Office plans not considering fresh air requirements
36. Thank You