Six Control Methods
Lowering Concentrations of Indoor Air Pollutants
Once it’s been determined that an IAQ problem
is either real, perceived, or a combination of multiple problems,
it’s time to develop a solution.
The EPA offers six basic control methods that
can lower concentrations of indoor air pollutants. Often, only a
slight shift in emphasis or action using these control methods is
needed to control IAQ more effectively.
1. Source Management – Managing pollutant
sources, the most effective control strategy, includes:
• Source removal — Eliminating or not
allowing pollutant sources to enter the school. Examples include
not allowing buses to idle, especially not near outdoor air intakes,
not placing garbage in rooms with HVAC equipment, and replacing
moldy materials.
• Source reduction — Improving technology
and/or materials to reduce emissions. Examples include replacing
2-stroke lawn and garden equipment with lower emitting options
(e.g., manual or electrically powered or 4-stroke); switching to low
emissions portable gasoline containers; and implementing technology
upgrades to reduce emissions from school buses.
• Source substitution — Replacing pollutant
sources. Examples include selecting less- or non-toxic art materials
or interior paints.
• Source encapsulation — Placing a barrier
around the source so that it releases fewer pollutants into the
indoor air. Examples include covering pressed wood cabinetry with
sealed or laminated surfaces or using plastic sheeting when
renovating to contain contaminants.
2. Local Exhaust — Removing (exhausting fume
hoods and local exhaust fans to the outside) point sources of indoor
pollutants before they disperse. Examples include exhaust systems
for restrooms and kitchens, science labs, storage rooms, printing
and duplicating rooms, and vocational/industrial areas (such as
welding booths and firing kilns).
3. Ventilation — Lowering pollutant
concentrations by diluting polluted (indoor) air with cleaner
(outdoor) air. Local building codes likely specify the quantity
(and sometimes quality) of outdoor air that must be continuously
supplied in. Temporarily increasing ventilation as well as properly
using the exhaust system while painting or applying pesticides,
for example, can be useful in diluting the concentration of noxious
fumes in the air.
4. Exposure Control — Adjusting the time and
location of pollutant exposure. Location control involves moving
the pollutant source away from occupants or even relocating
susceptible occupants.
a. Time of use — Avoid use of pollutant
sources when the building is occupied. For example, strip and wax
floors (with the ventilation system functioning) on Friday after
school is dismissed. This allows the floor products to off-gas over
the weekend, reducing the level of pollutants in the air when the
school is reoccupied on Monday. Another example is to mow around the
building and near play fields only before or after school hours.
b. Amount of use — Use air-polluting sources
as little as possible to minimize contamination of the indoor air.
c. Location of use — Move polluting sources as
far away as possible from occupants or relocating susceptible
occupants.
5. Air Cleaning — Filtering particles and
gaseous contaminants as air passes through ventilation equipment.
This type of system should be engineered on a case-by-case basis.
6. Education
— Teaching and training school occupants about IAQ issues.
People can reduce their exposure to many pollutants by understanding
basic information about their environment and knowing how to
prevent, remove, or control pollutants. Some solutions, such as
major ventilation changes, may not be practical to implement due
to lack of resources or the need for long periods of non-occupancy
to ensure the safety of the
occupants and staff. Use temporary measures to ensure good IAQ in
the mean-time. Other solutions, such as anti-idling programs, offer
low-cost options that can be easily and quickly implemented.
Specific lighting deficiencies or localized
sources of noise or vibration may be easily identified. Remedial
action may be fairly
straightforward, such as having more or
fewer lights, making adjustments for glare and relocating,
replacing, or acoustically insulating a noise or vibration
source. In other cases, where problems may be more subtle or
solutions more complex, such as psychogenic illnesses
(originating in the mind), enlist the services of a qualified
professional.
Remedial actions for lighting and noise
problems can range from modifications of equipment or
furnishings to renovation of the building. Reducing stress for
school staff may involve new management practices, job redesign,
or resolution of underlying labor-management problems.
Reducing stress for school staff may
involve new management practices, job redesign, or resolution of
underlying labor-management problems.
Evaluating Solutions
To help ensure a successful solution,
evaluate mitigation efforts at the planning stage by considering
the following criteria:
• Permanence;
• Durability;
• Operating principle;
• Installation and operating cost;
• Control capacity;
• Ability to institutionalize the
solution; and
• Conformity with codes.
Permanence
Mitigation efforts that
create permanent solutions to indoor air problems are clearly
superior to those that provide temporary solutions, unless the
problems are also temporary. Opening windows or running air
handlers on full outdoor air may be suitable mitigation
strategies for a temporary problem, such as off-gassing of
volatile compounds from new furnishings, but they are not
acceptable permanent solutions because of increased costs for
energy and maintenance. A permanent solution to microbiological
contamination involves cleaning and disinfection as well as
moisture control to prevent regrowth.
Durability
IAQ solutions that are
durable are more attractive than approaches that require
frequent maintenance or specialized skills. New items of
equipment should be quiet, energy-efficient, and durable.
Operating Principle
The operating principle of
the IAQ solution needs to make sense and be suited to the
problem. If a specific point source of contaminants is
identified, treatment at the source by removal, sealing, or
local exhaust is a more appropriate correction strategy than
diluting the contaminant with increased ventilation.
If the IAQ problem is
caused by outdoor air containing contaminants, then increasing
the outdoor air supply will only worsen the situation, unless
the supply of outdoor air is cleaned.
Durability
IAQ solutions that are durable are more
attractive than approaches that require frequent maintenance or
specialized skills. New items of equipment should be quiet,
energy-efficient, and durable.
Operating Principle
The operating principle of the IAQ
solution needs to make sense and be suited to the problem. If a
specific point source of contaminants is identified, treatment at
the source by removal, sealing, or local exhaust is a more
appropriate correction strategy than diluting the contaminant
with increased ventilation.
If the IAQ problem is caused by outdoor
air containing contaminants, then increasing the outdoor air
supply will only worsen the situation, unless the supply of
outdoor air is cleaned.
