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http://www.dllr.state.md.us/labor/iaq.htm
INDOOR AIR QUALITY
Introduction
This pamphlet is designed
to point out potential problems related to indoor air quality, review steps
that building owners and managers can take to investigate and correct
problems, and assist in obtaining additional help with indoor air quality
issues.
History
Over the past 40 years, a
revolution has taken place in building design and construction. Modern
buildings have been compared to spaceships, with self-contained ventilation
systems designed to provide a closely controlled environment that created
nearly optimum conditions for most occupants.
Then came the "energy
crisis". To reduce energy costs, buildings were better insulated and
computerized controls were added to reduce the use of heated air during
non-use hours. At the same time, synthetic components replaced traditional
natural building materials. Buildings "sealed" or insulated to preserve
conditioned air also preserved and concentrated the air contaminants
released by building components and operations. The ventilation systems
also became breeding grounds for microorganisms. Both air contaminants and
microorganisms were recirculated throughout the building.
As the work force shifts
from manufacturing to the service industries, "indoor air pollution" and
"sick building syndrome" have become concerns for an increasing number of
employees. Building owners and managers are being challenged to respond to
these concerns.
What Are the Problems?
The National Institute of
Occupational Safety and Health (NIOSH) reports that several factors
contribute to poor indoor air quality. They include inadequate ventilation,
air contaminants from inside the building, air contaminants from outside the
building, microbial contamination, contamination from the building fabric,
and other unknown causes.
·
Thermal
Environment. When many occupants complain about poor indoor air quality or
"stuffiness", they actually may be referring to comfort conditions such as
temperature or relative humidity. For example, warm, dry air in winter may
elicit symptoms of dry throat, coughs, or upper respiratory irritation in
much the same way as chemical or biological air contaminants.
Thermal
comfort is dependent on many factors, including:
Ø
Clothing
Ø
Activity
levels
Ø
Air
movement
Ø
Radiation
Ø
Air
temperature
·
Air
Contaminants. These can be divided into two categories: particulate, which
can include solids and fine droplets (mist), and gas and vapor.
Large particulate, which
often comprise visible dust, usually is filtered by a person's respiratory
system and often can lead to upper respiratory complaints. Smaller
particulate, which often is invisible, can behave much like a gas and may be
deposited in the lungs. Particles of concern include tobacco smoke,
asbestos fibers, and business machine chemicals. Dusts in general often are
referred to as nuisance dusts.
Gas and vapor can cause
health effects in several ways. They may be upper or lower respiratory
irritants or they may be absorbed into the bloodstream after respiration.
They may affect various parts of the body, causing headaches, nausea, and
dizziness. Gases of concern include carbon monoxide (CO) from combustion
sources; formaldehyde from paneling, particle board, carpeting, and
furniture; and volatile organic compounds (VOCs), the name for a wide
variety of chemicals from such items as adhesives, carpets, furniture, and
ceiling tiles.
·
Biological
Contaminants. This group can be subdivided into allergens, which include
fungi, spores, and insect parts and feces; and pathogens, bacteria and
viruses, which normally are contained in or on particulate matter. Although
many people are greatly concerned about exposure to pathogens such as
Legionnella bacteria (which causes “Legionnaires disease”), these
occurrences are very rare. In fact, many more people are affected by
allergens and develop sensitivities after a period of exposure.
What to Do?
When confronted with an
indoor air quality problem, the first reaction often is to "have the air
tested" in order to determine what is causing the problem. However, air
monitoring is expensive, and the results may be inconclusive for several
reasons. First, air contaminants often are found in very low levels.
Second, the effect of these contaminants in an office environment may be due
to the combined (synergistic) effects of two or more contaminants. Third,
the effects of biological contaminants cannot be correlated to exposure
levels. In short, many microorganisms are very common species. The fact
that they are detected in a building does not necessarily mean they are
causing harm.
If air monitoring is not
recommended, then what should be done? Several steps can be taken to
improve indoor air quality.
First, comfort
conditions, the thermal environment discussed previously, can be addressed
by ensuring recommended temperature and humidity levels. Recommended
temperature ranges are 68 to 76 degrees in winter, and 74 to 80 degrees in
summer. Relative humidity should be maintained within a range of 30% to
60%. Maintaining conditions within these ranges may eliminate complaints
without the necessity of taking other action.
The most important step,
however, is to ensure that building ventilation is as effective as
possible. Because symptoms often are related to a gradual buildup of
several air contaminants, one effective remedy is to dilute these unwanted
contaminants with outdoor air. Many ventilation systems include outside air
intakes. However, in an attempt to reduce energy costs, these intakes may
be partially or fully closed. Adjusting the supply of outdoor air to
recommended levels (15-20 cubic feet per minute, per occupant, for most
office areas) may be the most effective step in improving indoor air
quality. A qualified person should do such adjustments. In some cases,
this may require the expertise of a ventilation engineer.
The next step is to
ensure that air is circulated uniformly throughout the entire building.
Recommended routine inspection and maintenance of the system also is very
important. If building staff cannot perform these functions, a qualified
service contractor should be consulted.
It also may be possible
to reduce contaminants by eliminating sources within the building.
Information on cleaning and maintenance products should be reviewed to
ensure that the products are used properly and are not a source of odor or
contaminants. It is not unusual to find business machines such as
photocopiers in a small room with little or no ventilation, even when the
manufacturer recommends "adequate" ventilation or even exhaust ventilation.
Are building air intakes located near odor or contaminant sources such as
bathroom vents, loading docks, trash containers or exhaust vents or stacks?
If so, relocating the source of the contaminants may prove beneficial.
When investigating an
indoor air quality problem, it is important to solicit information from
building occupants. This can be done by questionnaires or by interviews.
Remember to keep occupants informed of corrective actions taken. Some
problems develop gradually. In the same way, corrections may produce only
subtle improvements. Let occupants know what steps you are taking.
Can Problems Be Avoided?
From time to time, office
interiors are renovated. Large rooms are subdivided. Open spaces are
partitioned into smaller areas. With proper planning and coordination, some
common pitfalls can be avoided.
When installing or
removing walls or partitions, note existing ventilation ductwork and
diffusers. Do these need to be relocated? Has hidden ductwork been
disconnected during renovation? Can low odor products be used in place of
odorous paints or adhesives? Are small renovation or maintenance jobs done
while office workers are not present, and is ventilation left in operation
overnight or during weekends to remove any solvent vapor, gas, or odor?
Vendors of office furniture and accessories often can provide information on
the release of formaldehyde or volatile organic compounds, especially for
large quantity purchases.
By taking proper
precautions during renovation and maintenance work, problems can be avoided.
Guides for Evaluating Indoor Air Quality
The following guides are
designed to assist in evaluating and correcting problems related to indoor
air quality.
Begin by completing the
"Building Ventilation Assessment." Answer all appropriate questions. The
information you gather here will prepare you for completing the "Building
Walk-Through Survey", which may reveal problems relating to indoor air
contaminants. The third guide, "Complaint Survey", is designed to assist you
in obtaining information from building occupants.
These guides may assist
in diagnosing problems and making necessary corrections. If you need
additional assistance from an outside source, the information you have
gathered will be valuable to the person you contact for assistance.
Additional help may be available from
private consultants with experience in indoor air quality evaluation, or
from MOSH Consultation Services (see Resourses, following).
Building Ventilation Assessment
It is important that the
building manager or other designated person be knowledgeable about the
operation of the building's ventilation system. The following information
will be useful in evaluating indoor air quality problems. The time and
effort used in obtaining the answers to these questions will be well spent.
Note that not all of the following questions apply to all systems.
By researching and
compiling this information, you should have a better understanding of how
your ventilation system is designed to perform and whether or not it is
performing as it was intended. You may identify areas that need
improvement. If so, ensure that an experienced, well-qualified ventilation
contractor is employed.
Building Characteristics
·
Building
age ___________
·
Number of
floors ________
·
Type of
windows (clear, tinted, etc.) _________________
Do windows open?
o
Yes
o
No
·
Who cleans
the building interior? ____________________________
How often?
_________________________
·
What is the
building layout? (i.e., open space, individual offices, combination)
________________________________________________________________
·
Has the building been
renovated?
o
Yes
o
No
If Yes, when?
_______________________________________________
What changes were made?
____________________________________
__________________________________________________________
·
Who is
responsible for the building:
Ø
management
______________________________________
Ø
maintenance
______________________________________
Ø
ventilation
(on-site or contractor) ______________________
Ventilation System
·
Heating
system __________________________________
·
Type of
fuel _____________________________________
·
Type of
heat (radiator, forced hot air, etc.)____________________________
·
Air
conditioning (central, zone, individual) ____________________________
Layout and Operation of System
·
Central air handling
units?
o
Yes
o
No
·
Area (zone) air handling
units?
o
Yes
o
No
·
Individual (window) air
handling units?
o
Yes
o
No
·
Plenum-type return
air?
o
Yes
o
No
·
Ducted return
air?
o
Yes
o
No
·
Return air at air handling
unit?
o
Yes
o
No
·
Does unit provide
continuous circulation? o
Yes
o
No
·
Is system air volume
constant?
o
Yes
o
No
·
Is system air volume
variable?
o
Yes
o
No
·
Does computer control
system?
o
Yes
o
No
If so, is performance
monitored?
o
Yes
o
No
By whom?
_________________________________________
How often?
_______________________________________
·
Does system provide
outside makeup air?
o
Yes
o
No
·
Are makeup air controls:
o
manual o
automatic
·
Who
inspects/adjusts makeup air controls? _____________________________
·
How much
make-up air is provided (CFM per person or % of makeup) ________
________________________________________________________________
·
Do the
following components receive routine inspection/maintenance?
Ø
Supply air
outlets
o
Yes
o
No
Ø
Filters
o
Yes
o
No
Ø
Thermostats/sensors
o
Yes
o
No
Ø
Coil condensation
pans
o
Yes
o
No
Ø
Internal duct
work
o
Yes
o
No
Ø
Dampers
o
Yes
o
No
Ø
Belts
o
Yes
o
No
If so, by whom
________________________________________
Ø
Is system equipped with a
humidifier? o
Yes
o
No
If so, what type?
_____________________________________
Ø
Can or do
occupants adjust:
Supply air
outlets
o
Yes
o
No
Thermostats
o
Yes
o
No
Other controls
(list)
o
Yes
o
No
_______________________________________________________
·
Are there
operations/processes/machines that can produce air contaminants?
o
Yes
o
No
If so, list them
__________________________________________________
·
Was the
ventilation system commissioned (tested on installation)?
o
Yes
o
No
·
Has the system ever been
balanced or adjusted?
o
Yes
o
No
If yes, by whom
____________________________________________
When
_____________________________________________
Is report
available?
o
Yes
o
No
·
Is there a smoking
policy?
o
Yes
o
No
Does it meet the requirements
of MOSH regulations? o
Yes
o
No
·
Has the volume of air, per
room occupant, been measured?
o
Yes
o
No
Note: The
American Society of Heating, Refrigerating, and Air Conditioning Engineers
(ASHRAE) currently recommends 15-20 cubic feet per minute (CFM), of outside
air, per occupant, for most office or public building environments.
·
What is the
efficiency of the filters for the ventilation system? _______________
________________________________________________________________
Note: Filters
usually are installed to protect equipment, not to improve air quality. If
not changed regularly, they slow the airflow and can become a source of
contaminants. With the advice of a qualified person, filters can be
upgraded to improve air quality.
Building Walk-Through Survey
In conducting a
walk-through survey, be alert for four general sources of contaminants, in
addition to ventilation system problems. These are:
·
chemical
sources from within the building
·
chemical
sources from outside the building
·
chemical
sources from the building fabric itself
·
microbial
contamination
Many people feel that the
first response to an indoor air contaminant problem should be to conduct air
monitoring. However, in many cases, the complaints of occupants may be a
result of inadequate ventilation. Air monitoring often is unnecessary or
non-conclusive because air contaminants may be present in levels too low to
monitor, or the symptoms of exposure may be the result of the combined
(synergistic) effects of contaminants. Also, improved ventilation may
successfully bring relief from the effects of air contaminants without air
monitoring.
In conducting your
building walk-through survey, be aware that although occupants may refer to
“poor air quality”, their complaints in fact may relate to other factors:
thermal comfort (too hot, too dry), poor work station design (poor posture
resulting in body aches), inadequate lighting (glare resulting in eye strain
or headaches), or stress (job-related or personal).
The following questions
highlight potential problem areas, which should be reviewed in your survey.
Ventilation System
·
Is each
office space equipped with one or more air supply ducts? Sometimes, space
is repartitioned and some rooms are left without ventilation sources.
o
Yes
o
No
·
Is air
flowing from supply air ducts? Ducts may be disconnected above a dropped
ceiling, air may not be flowing to the ends of a system or a fan may be
broken.
o
Yes
o
No
·
Have
occupants readjusted air outlets? Individual outlets may be opened or
closed, thus upsetting the balance of a larger system.
o
Yes
o
No
·
Are return
air grills kept open and clear? Boxes, cabinets, or other materials may
block air grates, usually located near a mechanical room.
o
Yes
o
No
·
Are
temperatures uniform throughout the building? The sun shining into windows
may make one side of a building warmer. Occupants may have readjusted
thermostats, or thermostats may need to be calibrated. Office partitions
may keep heated/cooled air from circulating, producing different
temperatures at ceiling and floor levels.
o
Yes
o
No
·
Are
maintenance personnel properly trained to perform routine inspection and
maintenance? On-site maintenance personnel may not be familiar with
equipment and manufacturer's recommendations, such as how often to change
filters or where filters are located.
o
Yes
o
No
Are routine inspections
and maintenance performed?
o
Yes
o
No
Sources of Contaminants
from Inside the Building
·
What
equipment may be producing contaminants? Photocopiers, video machines and
blueprint machines may release vapor or gas. The electrical components of
these machines may produce ozone.
________________________________________________________________
________________________________________________________________
·
Is a
chemical information list compiled, and are material safety data sheets
(MSDS) available? Maryland law requires that all employers make a list of
hazardous materials, and obtain a material safety data sheet for each
substance. This information can be a valuable resource in determining what
is used in a building.
o
Yes
o
No
·
Is there a
designated smoking area in the building? Cigarette smoke is considered to
be the largest contributor to poor indoor air quality.
o
Yes
o
No
·
Does the
designated smoking area have a separate exhaust system? If not, smoke may
be recirculated into non-smoking areas.
o
Yes
o
No
Note: MOSH regulations require that a
designated smoking area have a separate ventilation system that exhausts
directly to the outside without recirculating into non-smoking areas.
Sources of Contaminants
from Outside the Building
·
Can outside
contaminants be drawn into system air intakes? Inspect roof and outside
walls to determine if building exhaust or other source of contaminants is
near an air intake. Contamination sources can include exhaust vents
(bathrooms, machines, labs), dumpsters, idling vehicles, and air pollution
sources on adjoining property. Wind patterns can trap air contaminants on a
flat roofed building, so that contaminants are held and drawn into the
ventilation system. A higher exhaust stack may prevent re-entry into the
building. A rule-of-thumb guide is that an exhaust stack should be 10 feet
higher than an air intake located within 50 feet of the stack.
o
Yes
o
No
Sources of Chemical
Contaminants from the Building Fabric
·
Have new
furniture, carpets, or draperies been installed? These products can
"off-gas" or release volatile organic compounds (VOCs) for weeks or months
after installation.
o
Yes
o
No
·
Is
painting, carpet installation, or other repair or renovation performed
during periods of low occupancy? Paint solvents, carpet adhesives, and
other chemicals used by contractors can be odorous and irritating. By
working on weekends with maximum ventilation, or by substituting products,
discomfort can be minimized.
o
Yes
o
No
Microbial Contamination
Occupants often are quick
to suspect microbial contamination, although it is probably responsible for
a small minority of air quality problems. Microorganisms need water, food,
and a place to grow. Almost any dirty nook can become infested if it
becomes wet or damp. Sampling for microorganisms is expensive, requires
special expertise, and sampling results are difficult to translate into
solutions. Consequently, it is advisable to inspect for potential problem
areas, and clean and disinfect them, as a first step in addressing this
problem.
·
Do areas of
the building repeatedly become wet or damp? Porous materials, such as
carpets, draperies, ceiling tiles, fiberglass insulation, and filters can
become contaminated with microorganisms as a result of leaks in a roof,
wall, or plumbing. Porous materials cannot always be successfully
decontaminated, and sometimes must be replaced.
o
Yes
o
No
·
If damp
spots appear, are they promptly cleaned and disinfected? Cleaning alone may
not remove contamination. If dampness recurs, the dormant microorganisms
may become active. A variety of disinfectants are available for specific
uses. Ensure that the disinfectant is used properly.
o
Yes
o
No
·
Are leaks
promptly repaired? Some leaks, especially on a flat roof, present a real
challenge. Money saved on a cheap roof repair may be spent many times over
on building repairs when a leak recurs.
o
Yes
o
No
·
Do humidity
levels exceed 60% in occupied spaces? High humidity in buildings can mean
that air ducts become wet with condensation. Air ducts that are lined with
fiberglass for noise damping are especially prone to contamination.
o
Yes
o
No
·
Are air
conditioning units with condensation coils equipped with a collection pan
and drain? This should be part of routine inspection and maintenance.
Each air conditioning unit should be regularly inspected, and if the drains
are clogged, they should be repaired, cleaned and disinfected. Central,
area, and window air conditioners are prone to clogged drains.
o
Yes
o
No
·
Is the
ventilation system equipped with a humidifier? A dedicated, "dry steam"
humidifier is preferable to steam from a boiler system, which can be
contaminated by corrosion inhibitors. It is recommended that systems not
use recirculated water. Cold water humidifiers, especially, require regular
inspection, cleaning and disinfection.
o
Yes
o
No
·
Is the
building equipped with a water spray or cooling tower? These systems
require regular inspection, treatment, and maintenance.
o
Yes
o
No
·
Are filters
regularly inspected and changed? Dirty filters can become infected with
microorganisms. Change them according to manufacturer's specifications, or
more frequently as needed.
o
Yes
o
No
