Indoor Air Ventilation Standards; Co Based Demand Control Ventilation - Honeywell Design and Application Technical Reference Manual

ASHRAE is continually updating the
ventilation standard (ASHRAE 62.1) to provide
guidelines for design and maintenance of
buildings. These standards are recommended
guidelines only and are not legal
requirements. However many state and local
codes use the ASHRAE standards as the
basis for building codes for new construction
and building occupancy. They also form a
basis for litigation in indoor air quality lawsuits.
Some measurements and gases referred to in
the standards may not be familiar to the
average person in the HVAC industry.
However the majority of the information
contained in these standards is very clearly
stated. Everyone in the HVAC industry should
be knowledgeable about the contents of these
standards.
The ventilation standard states a minimum
outdoor air ventilation rate required per person
per type of environment in Cubic Feet per
Minute (cfm). The ventilation requirement
varies between occupied and unoccupied
periods. Outdoor air dampers are set to a
minimum position based on the maximum
occupancy level for the space. To save energy
the ASHRAE 62.1 standard also allows
ventilation to be based on a CO
that determines occupancy. This is commonly
referred to as CO -based demand control
2
ventilation (DCV).
CO Based Demand Control
2
Ventilation
CO is a fairly dependable indicator of the
2
concentration of the odorous bioeffluents
exhaled by human beings. Therefore we can
use CO concentration levels in a space to
2
determine the human occupancy and reduce

Indoor Air Ventilation Standards

sensor input
2
outdoor air intake when the space is not
occupied to the maximum design occupancy
level. CO -based DCV is an energy
2
conservation measure; its purpose is to
reduce outdoor air intake rates and the energy
required to condition the outdoor air when
spaces are not occupied at maximum design
densities.
For those who do not want to read an
engineering standard, ASHRAE offers a user
manual that:
• offers information on the intent and
application of Standard 62.1
• provides sample calculations and examples.
• provides useful reference materials.
• gives guidance to building operation and
maintenance personnel.
Standard 62.1 Ventilation
for Acceptable Indoor Air Quality
(ANSI Approved)
The Standard and User's Manual can be
ordered from:
ASHRAE Publications Sales
1791 Tullie Circle, N.E.
Atlanta, GA 30329 or
www.ashrae.org
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Section 1 - Ventilation
Honeywell Economizers 63-8594-02