Appendix C 407
recommended range of illuminance is a function of the type of visual
activity and the age of the occupants. Guidelines also provide recom-
mendations for the maximum luminance ratio, i.e., range of luminance
in the visual field. Occupants satisfaction with lighting may vary with
illuminance and with the characteristics of the lighting system (Katzev
1992).
4.4 INDOOR POLLUTANTS, THEIR SOURCES,
AND HEALTH EFFECTS
There are a large number of indoor air pollutants that can influ-
ence occupant health and the perceived acceptability of indoor air. The
following paragraphs introduce these pollutants.
Gaseous human bioeffluents—Humans release a variety of odor-
ous gaseous bioeffluents, e.g., body odors, which influence the perceived
acceptability of indoor air. Historically, most standards and guidelines
for minimum ventilation rates in buildings have been based primarily
on the ventilation needed to maintain indoor air acceptable to a large
proportion (e.g., 80%) of visitors when they initially enter a space with
occupants as the only indoor pollutant source. In the last decade, con-
cerns about other sources of odors and adverse health effects from air
pollutants have increasingly influenced building ventilation standards.
Carbon Dioxide (CO 2 ) is one of the gaseous human bioeffluents
in exhaled air. Humans are normally the main indoor source of carbon
dioxide. Unvented or imperfectly vented combustion appliances can
also increase indoor CO 2 concentrations. The outdoor CO 2 concentra-
tion is often approximately 350 ppm^1 , whereas indoor concentrations
are usually in the range of 500 ppm to a few thousand ppm. At these
concentrations, CO 2 is not thought to be a direct cause of adverse
health effects; however, CO 2 is an easily-measured surrogate for other
occupant-generated pollutants, such as body odors.
The indoor CO 2 concentration is often used, sometimes inappropri-
ately, as an indicator of the rate of outside air supply per occupant. If
the number of occupants and the rate of outside air supply are constant
and the CO 2 generation rate of occupants is known, the rate of outside
air supply per occupant is related to the equilibrium indoor CO 2 con-
centration in a straightforward manner as predicted by a steady-state
- In urban areas, outdoor CO 2 concentrations may substantially exceed 350
ppm and vary considerably with time.