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:

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