Carbon monoxide alarms are now required residential equipment and assumptions regarding air leakage are substantially different under a new ASHRAE regulation.

The American Society of Heating, Refrigeration and Air-Conditioning Engineers recently published an update to its standard 62.2, “Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings.” A major change from the 2010 version is the increase in the mechanical ventilation rate to 7.5 cubic feet per minute per person, plus 3 cfm per each 100 feet.

The previous standard assumed 2 cfm per 100 square feet, said Don Stevens, chairman of the committee that revised the rule.

“Because research shows houses have gotten tighter and apartments have always been tight, the 2013 edition drops this default assumption and calls for the entire amount to be provided mechanically,” he said. “The only exception is when single-family homes have a blower-door test. Then the predicted average annual leakage rate can be deducted.”

Another major change is the requirement that all homes install carbon monoxide detectors. CO poisoning causes hundreds of deaths and thousands of injuries each year, said Paul Francisco, vice chairman of the ASHRAE committee. The change has been discussed for many years, and a number of states already require the devices.

“Residents have very little ability to sense the presence of CO without detectors, unlike many other indoor polluting events,” he said.

A copy of the full standard is available for $58 by calling (800) 527-4723 or visiting www.ashrae.org/bookstore. The price is $48 for society members.