Indoor Air Quality Case StudiesKevin Renton

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

Bad Parenting ????or …….

Occupational Health Risk AssessmentWhat to do?

eyes, nose, and throat irritation, headaches, dizziness & fatigue

Season Parameter Measurement

Winter or Summer CO2 Less than 1000ppm

Winter Temperature 20-24°C

Summer Temperature 23-26°C

Winter or Summer Humidity 30-60% RH

Table 1: Acceptable Indoor Air Quality – ASHRAEGood 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.

Parameter Reference values Source Temperature 23-26 °C ASHRAE Standard 62-1989,

1992

Humidity 30-60% RH ASHRAE Standard 62-1989, 1992

Carbon Monoxide 8 hour 9 ppm ASHRAE Standard 62-2000Carbon Dioxide less than 1000 ppm ASHRAE Standard 62-1989,

1992

Number of air changes/hour

6 air changes/hour: offices D. Jeff Burton

8-12 air changes/hour: medical centre & medical offices

Engineering toolbox – see references below

Total air supply required per person

10 L/sASHRAE 62-2001

Comfort Less than 10% complaining of any one thermal

condition-hot/cold/stale/humid

ASHRAE 55

GUIDELINES USED

Contaminant Typical sources Level of interest Comments

Carbon monoxide(CO)

Leaking vented combustion appliancesUnvented combustion appliancesParking garagesOutdoor air

3 ppm above outdoor level9 ppm(health)

Mental alertness level an indication of abnormal indoor concentration; investigation of possible sources advisableHealth level based on effects on persons with coronary artery disease, average exposure for 8 hours over a working lifetime.

Formaldehyde(HCHO)

Pressed wood productsFurniture and furnishings

120.μg/m³( 0.1 ppm)

Based on irritation of sensitive people, 30 minute exposure(WHO).

Lead (Pb) Paint dust Outdoor air

1.5 μg /m³ Based on adverse effects on neuropsychological functioning of children, average exposure for 3 months (WHO: 0.5-1 μg/m³ for 1 year)

Nitrogen dioxide (NO2)

Leaking vented combustion appliancesUnvented combustion appliancesOutdoor Air

100μg/m³ Based on providing protection against adverse respiratory effects, average exposure for one year

Odors OccupantsFungal ( mold ) sourcesVOC sourcesOutdoor air

Predicted acceptability to 80 % or more of occupants or visitors

CO2 concentration can be used as a surrogate for occupant odor (odorous bioeffluents ). For sources other than people, source control is recommended.

Ozone (O3) Electrostatic appliances Office machines Ozone generatorsOutdoor air

100μg/m³( 50 ppb)

Based on potential for adverse acute and chronic effects and an additional margin of protection, 8 hour exposure.

Particles (PM10)

Dust Smoke Deteriorating materialsOutdoor air

50μg/m³ Based on protecting against respiratory morbidity in the general population and avoiding exacerbation of asthma, average exposure for one year, no carcinogens. Indoor concentrations are normally higher than outdoor concentrations, the guideline level may lead to unacceptable deposition of dust.

Contaminant Typical sources Level of interest Comments

Radon (Rn) Soil gas 4 pCi/liter Based on lung cancer, average exposure for 1 year.

Sulfur dioxide (SO2)

Unvented space heaters ( kerosene)Outdoor air

80μg/m³ Based on protecting against respiratory morbidity in the general population and avoiding exacerbation of asthma, average exposure 1 year.

Total volatile organic compounds ( TVOC’s)

New building materials and furnishingsConsumable products Maintenance materialsOutdoor air

<300μg/m³ - comfort range complaints unlikely300-3000μg/m³ - complaints possible>3000μg/m³ - discomfort range, complaints likely> 25000μg/m³ - toxic range

Odor and irritation responses to organic compounds are highly variable. The three guidelines for this class of compounds represent ranges where odor and irritation complaints are seldom observed (comfort range); where complaints become significant in buildings (comfort/discomfort range); and where significant complaints are likely (discomfort range). Average indoor concentrations in most buildings are well below 1000μg>m³. The value for design should be selected by the designer and the owner of the building. During the operation of the building, measured TVOC concentrations above 1000μg>m³should trigger further analysis to determine whether concentrations of individual compounds are above levels of concern. Above 25 mg/m³ additional neurotoxic effects other than headaches will occur.

Case Studies: Sixty Practical Applications of OH&S Control Principles

(Elemental industrial hygiene series) Dr. Jeff Burton

• Are these complaints suggestive of a biological contamination of some sort?

• What complaint rate is suggestive of a real IAQ problem?

• 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.

What potential sources would the IH investigate (and eliminate)?

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.

What would be likely source of these complaints, given that complaints were isolated to two floors and complaints began at the beginning of summer?

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.

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)

• Indoor air temperatures and humidities were at the upper end of normal:

23- 24 deg C55-65% relative humidity

• Indoor carbon dioxide samples were not abnormally high – av 900ppm

• Outdoor air concentrations of carbon dioxide av 370ppm

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)

• 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

IAQ Complaints in an Older Office Building

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.

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

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.

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."

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.

. Average indoor measured dry bulb temperature = 23° C; range = 20 -24°C; RH = 30-50%.

70 792 litre/min

33 l/s person

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.

A new building was being constructed on the west side of the building.

Outside: Stormy; west winds at 10 mph, outside temperature, 40°F, RH, near 100%.

Building construction: Concrete block; aluminium windows; 25 years old.

.

. The building was quiet dusty; housekeeping was performed weekly during the evenings.

. The AHU had no provision for humidifying the air.

Please evaluate the above data and write your- responses to the

following questions1. Was there a genuine IAQ problem?

2. Were the following IAQ-related parameters okay/not okay?

Air distribution?

Total air volume flowrates?

OA delivery?

Carbon Dioxide Concen trations?

Thermal Comfort conditions?

Air contaminants?

Air contaminant concentrations?

HV AC problems?

What do think may be the sources and/or causes of the complaints?

List possible contributing factors.

List possible corrective actions or controls.

 

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 cfm and 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.

Recommendations for control:

-- Rebalance the HV AC system to bring the building into a slight positivepressure (re: the outside).

-- Maintain tight control of remodeling /renovation activities in the future.

INDOOR AIR QUALITY SAMPLING WORKSHEET

Room number and descriptionCO RH TEMP CO2

Comments

ppm % °C ppm

Office worker 1 0.9 28.2 22.5 918

Open plan office, which accommodates about 36 people. The air-conditioning system used does not introduce fresh air from the outside rather it recirculates the air from inside the building. The office has carpet flooring, that has to date this year been washed only once and it is vacuumed every second day with a vacuum cleaner fitted only with an ordinary dust filter. The partitioning on the workstation has cotton fabric on it. The office has openable windows but they are seldom opened and they were not opened on the day of the assessment. The office has about 4 pot plants. Smoking was observed on 2 of the 4 balconies.

Office worker 2 0.6 27.7 22.7 958

Office worker 3 0.7 28.2 22.6 969

Office worker 4 0.6 28.0 22.4 963

Outside (back of building by fire escape door) 0.1 18.2 20.9 369

Outside (front of building by entrance) 0.1 12.5 26.0 348

INDOOR AIR QUALITY SAMPLING WORKSHEETRoom number and description CO RH TEMP CO2

Comments

ppm % °C ppm

Microbiology/ recieving 0.1 24.3 21.6 776

Store room 0.0 23.3 21.5 675

Flow cytometery 0.0 21.3 21.2 556

Lab Manager 0.0 20.4 21.0 519

Tea room 0.0 21.2 20.8 532

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.

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

Thank You