Standard 62.1 – 2010
Ventilation for Acceptable Indoor Air Quality


ASHRAE Standard 62.1-2010, Ventilation for Acceptable Indoor Air Quality, specifies minimum outside air ventilation rates based on space use, occupancy and floor area. The Standard also requires that outside airflow rates exceed exhaust airflow rates (net positive mechanical exfiltration) during periods of dehumidification (cooling) to limit the infiltration of high dew point outside air. The infiltration of high dew point outside air will result in poor humidity and temperature control and may lead to mold growth in the building envelope. Proper pressurization also reduces unfiltered dirt and dust in the outside air from entering a building. Intake flow rates should be monitored with permanently mounted airflow measuring devices to assure minimum compliance with the Standard for ventilation and building pressurization.



Outside air intakes are traditionally very low velocity (<<400 FPM) and have limited straight run of uniform duct between an intake louver and control damper. Pitot arrays and other differential pressure measuring devices as well as vortex shedders cannot be properly applied on most outside air intakes because of the flow rate and space limitations. Thermal dispersion technology, as manufactured by EBTRON, is well suited for the direct measurement of outside airflow measurement. EBTRON pioneered direct outside air intake flow measurement in the late 1980's.

Depending on the level of sophistication of the controls on the air handling system, the monitored outside air intake flow rates may be used as an input to a control device for output to modulating control damper actuators and/or variable speed fans to maintain the desired intake flow rate. For more information on control strategies for minimum outside air intake control refer to the section on this web site for Control Strategies or contact EBTRON's application engineering department or your local EBTRON representative.

If outside airflow rates are not controlled, they should be setup for worst-case ventilation rates in accordance with the Ventilation Rate Procedure (VRP) of ASHRAE 62.1. The use of a low flow alarm is recommended and a requirement of IEQ Credit 1 (1 point) of LEED 2009, a mandatory prerequisite for CS and Healthcare in proposed LEED BD&C 2012, a partial requirement for LEED EB:O&M 2012 for Enhanced IAQ Strategies EQ credit with 2 points and the mandatory provisions of ASHRAE Standard 189.1-2009, Standard for the Design of High Performance Buildings.

Benefits of continuous monitoring/control of outside air intake flow rates include:

  • Compensation for pressure variations on the intake system including wind and stack effect and changes in mixed air plenum pressure on VAV systems. {tech bulletin coming soon}

  • Compensation for (or detection of) control damper issues including linkage hysteresis, seal deterioration and binding. {tech bulletin coming soon}

  • Maintenance of proper building pressure. {tech bulletin coming soon}

  • Optimized CO2 demand controlled ventilation (DCV). {tech bulletin coming soon}

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Link to ASHRAE Standards

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