Indoor air quality

Good IAQ: a clean, healthy, and odor-free indoor environment.

“Sick Building Syndrome” (SBS) is discomfort/illness caused by indoor air. SBS is often comparable to a cold or influenza

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A few facts about poor IAQ:

Health problems: 30 — 70 million people (U. S. EPA)

Health complaints: 30% new and remodeled buildings (U. S. EPA) Occupational illness: 439,000 cases in 1996 (NIOSH)

Economic loss: $40 — 120 billion/year ($200-600/person. year)

Causes of sickness:

• COx, NOx and other common gases (human, combustion)

• Environmental tobacco smoke ETS (smoking)

• Volatile organic compounds VOC

(building materials: construction materials, furnishings, finishes)

• Particulate matters (outdoor air, activities, ETS)

• Biohazards (molds, bacteria, etc.)

• Radon (soil)

Contaminants

Sources

Permitted level

Health effects

Co2

Human, combustion

1000 ppm

Stuffing

CO

Combustion, ETS

15 ppm

Body chemistry

Sox

Combustion

Irritation, asthma

NOx

Combustion

100 |ig/m3

Not very clear

Ra

Soil

4 picocuries/1

Lung cancer

VOCs

Combustion,

0.1 ppm

Eyes and mucous

(Formaldehyde)

Pesticides, building materials, etc.

Membrane irritation

Particulate

Outdoor air,

Lung diseases

(0.01 micro-insects)

Activities, ETS, furnishings, pets, etc

Cancer (ETS)

The following diagram illustrates the buildup of indoor carbon dioxide (due to occupant exhalation) throughout a normal day:

Indoor air quality

Carbon Dioxide Concentration (ppm)

Results

250-350

Normal outdoor ambient air

600

Minimal air quality complaints

600-1000

Effect on indoor air quality is less clearly interpreted

1000

Indicates inadequate ventilation; indoor air quality complaints are more widespread

Common Causes of Poor Indoor Air Quality (IAQ)

Tight buildings (Energy conservation)=>

=>Less outdoor air (Infiltration) =>

=>High contaminant concentrations (New building materials release VOCs)

Numerous indoor air quality investigations over the last decade by the National Institute for Occupational Safety & Health (NIOSH) have found the primary source of indoor air quality problems are:

Inadequate ventilation 52%

Contaminant from inside the building 16%

Contaminant from outside the building 10%

Microbial contamination 5%

Contamination from building fabric 4%

Unknown Sources 13%

Control of contaminants

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New parameters

Supply air — Total air supplied to a space

Fresh air — Outdoor air

Infiltration — Uncontrolled air entered to a space

Exfiltration — Uncontrolled air left a space

For mechanical ventilated space, infiltration should be zero because of positive pressure in the conditioned space.

Ventilation

Most common method for contaminant control is ventilation. Ventilation can be either natural or forced. Ventilation dilutes contaminants with outdoor air, and requirements are defined by state/local codes and referenced standards.

ANSI/ASHRAE Standard 62-1999:

Ventilation for Acceptable Indoor Air Quality

Defines:

• Acceptable outdoor air quality

• Procedure for acceptable ventilation

Posted in Fundamentals of Heating. Ventilating, and Air-Conditioning


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