Transcript Indoor Air Quality Case Studies - Kevin Renton

Indoor Air Quality Case Studies
Kevin 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 …….
eyes, nose, and throat irritation, headaches, dizziness &
fatigue
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.
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
GUIDELINES USED
Parameter
Reference values
Source
Temperature
23-26 °C
Humidity
30-60% RH
Carbon Monoxide
Carbon Dioxide
8 hour 9 ppm
less than 1000 ppm
Number of air
changes/hour
6 air changes/hour: offices
ASHRAE Standard 62-1989,
1992
ASHRAE Standard 62-1989,
1992
ASHRAE Standard 62-2000
ASHRAE Standard 62-1989,
1992
D. Jeff Burton
8-12 air changes/hour: medical
centre & medical offices
Engineering toolbox – see
references below
Total air supply
required per person
Comfort
10 L/s
Less than 10% complaining of
any one thermal conditionhot/cold/stale/humid
ASHRAE 62-2001
ASHRAE 55
Contaminant
Typical sources
Level of interest
Comments
Leaking
vented
combustion
appliances
Unvented
combustion
appliances
Parking
garages
Outdoor air
Formaldehyde Pressed wood
(HCHO)
products
Furniture and
furnishings
Lead (Pb)
Paint dust
Outdoor air
3 ppm above
outdoor level
9
ppm(health)
Mental alertness level an indication of abnormal
indoor concentration; investigation of possible
sources advisable
Health level based on effects on persons with
coronary artery disease, average exposure for 8
hours over a working lifetime.
120.μg/m³
( 0.1 ppm)
Based on irritation of sensitive people, 30 minute
exposure(WHO).
1.5 μg /m³
Nitrogen
Leaking
dioxide (NO2) vented
combustion
appliances
Unvented
combustion
appliances
100μg/m³
Based on adverse effects on neuropsychological
functioning of children, average exposure for 3
months (WHO: 0.5-1 μg/m³ for 1 year)
Based on providing protection against adverse
respiratory effects, average exposure for one year
Carbon
monoxide
(CO)
Odors
Occupants
Fungal (
mold )
sources
VOC sources
Outdoor air
Ozone (O3)
Electrostatic 100μg/m³
appliances
( 50 ppb)
Office
machines
Ozone
generators
Outdoor air
Dust
50μg/m³
Smoke
Deteriorating
materials
Outdoor air
Particles
(PM10)
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.
Based on potential for adverse acute and
chronic effects and an additional margin
of protection, 8 hour exposure.
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.
80μg/m³
Based on protecting against respiratory morbidity in
the general population and avoiding exacerbation of
asthma, average exposure 1 year.
<300μg/m³ comfort range
complaints
unlikely
3003000μg/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.
Sulfur
dioxide
(SO2)
Unvented
space heaters
( kerosene)
Outdoor air
Total volatile New building
organic
materials and
compounds ( furnishings
TVOC’s)
Consumable
products
Maintenance
materials
Outdoor air
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 C
55-65% 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."
. 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; 70 792 33 l/s person
litre/min
percent OA 30%; the amount of air being returned
to the AHU, QRA = 3,000 cfm.
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.
.
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 questions
1. Was there a genuine IAQ problem?
2. Were the following IAQ-related parameters
okay/not okay?
Air distribution?
Total
air
flowrates?
OA delivery?
volume
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 positive
pressure (re: the outside).
--
-- Maintain
tight control of remodeling /renovation
activities in the future.
INDOOR AIR QUALITY SAMPLING WORKSHEET
Room number and description
CO
RH
TEMP
CO2
ppm
%
°C
ppm
Office worker 1
0.9
28.2
22.5
918
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
Comments
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.
INDOOR AIR QUALITY SAMPLING WORKSHEET
Room number and
description
Comments
CO
RH
ppm %
TEMP
CO2
°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