ASTM D6245-12
Standard Guide for Using Indoor Carbon Dioxide Concentrations to Evaluate Indoor Air Quality and Ventilation

Standard No.

ASTM D6245-12

Release Date

2012

Published By

American Society for Testing and Materials (ASTM)

Status

Be replaced

Replace By

ASTM D6245-18

Latest

ASTM D6245-18

Scope

Indoor CO₂ concentrations have been described and used by some people as an indicator of indoor air quality. These uses have included both appropriate and inappropriate interpretations of indoor CO₂ concentrations. Appropriate uses include estimating expected levels of occupant comfort in terms of human body odor, studying occupancy patterns, investigating the levels of contaminants that are related to occupant activity, and screening for the sufficiency of ventilation rates relative to occupancy. Inappropriate uses include the application of simple relationships to determine outdoor air ventilation rates per person from indoor CO₂ concentrations without verifying the assumptions upon which these relationships are based, and the interpretation of indoor CO₂ concentrations as a comprehensive indicator of indoor air quality.

Outdoor air ventilation rates affect contaminant levels in buildings and building occupants' perception of the acceptability of the indoor environment. Minimum rates of outdoor air ventilation are specified in building codes and indoor air quality standards, for example, ASHRAE Standard 62. The compliance of outdoor air ventilation rates with relevant codes and standards are often assessed as part of indoor air quality investigations in buildings. The outdoor air ventilation rate of a building depends on the size and distribution of air leakage sites, pressure differences induced by wind and temperature, mechanical system operation, and occupant behavior. Given all of this information, ventilation rates are predictable; however, many of these parameters are difficult to determine in practice. Therefore, measurement is required to determine outdoor air change rates reliably.

The measurement of CO₂ concentrations has been promoted as a means of determining outdoor air ventilation rates per person. This approach, referred to in this guide as equilibrium analysis, is based on a steady-state, single-zone mass balance of CO₂ in the building and is sometimes presented with little or no discussion of its limitations and the assumptions on which it is based. As a result, in some cases, the technique has been misused and indoor CO₂ concentration measurements have been misinterpreted.

When the assumptions upon which equilibrium analysis is based are valid, the technique can yield reliable measurements of outdoor air ventilation rates. In addition, indoor CO₂ concentrations can be used to determine other aspects of building ventilation when used properly. By applying a mass balance at an air handler, the percent outdoor air intake in the supply airstream can be determined based on the CO₂ concentrations in the supply, return, and outdoor air. This percentage can be multiplied by the supply airflow rate of the air handler to yield the outdoor air intake rate of the air handler. In addition, the decay of indoor CO₂ concentrations can be monitored in a building after the occupants have left to determine the outdoor air change rate of the building.

Continuous monitoring of indoor and outdoor CO₂ concentrations can be used to study some aspects of ventilation system performance, the quality of outdoor air, and building occupancy patterns.

1.1 This guide describes how measured values of indoor carbon dioxide (CO₂) concentrations can be used in evaluations of indoor air quality and building ventilation.

1.2 This guide describes the determination of CO₂ generation rates from people as a function of body size and level of physical activity.

1.3 This guide describes the experimentally-determined relationship between CO₂ concentrations and the acceptability of a space in terms of human body odor.

1.4 This guide describes the following uses of indoor CO₂

ASTM D6245-12 Referenced Document

• ASTM D1356 Standard Terminology Relating to Sampling and Analysis of Atmospheres*， 2024-04-19 Update
• ASTM D3249 Standard Practice for General Ambient Air Analyzer Procedures
• ASTM E741 Standard Test Method for Determining Air Change in a Single Zone by Means of a Tracer Gas Dilution

ASTM D6245-12 history

• 2018 ASTM D6245-18 Standard Guide for Using Indoor Carbon Dioxide Concentrations to Evaluate Indoor Air Quality and Ventilation
• 2012 ASTM D6245-12 Standard Guide for Using Indoor Carbon Dioxide Concentrations to Evaluate Indoor Air Quality and Ventilation
• 2007 ASTM D6245-07 Standard Guide for Using Indoor Carbon Dioxide Concentrations to Evaluate Indoor Air Quality and Ventilation
• 1998 ASTM D6245-98(2002) Standard Guide for Using Indoor Carbon Dioxide Concentrations to Evaluate Indoor Air Quality and Ventilation
• 1998 ASTM D6245-98 Standard Guide for Using Indoor Carbon Dioxide Concentrations to Evaluate Indoor Air Quality and Ventilation