Idling a Vehicle in an Attached Garage

Warming up or running an engine with the garage door closed.

47Moderate burden · out of 100

Cleaner swapReverse out first, and never run an engine in a closed garage

How this score is built

100Start
63.2Chemical hazard 8 × 4.6−36.8
49.6Everyday exposure 4 × 3.4−13.6
47Persistence 1 × 2.6−2.6
ModerateThe band47 sits in 40–59.

What each input rests on

The three ratings behind the score, and the studies each rests on
Input	Rating	Evidence
Chemical hazard	8/10	unsourced input
Everyday exposure	4/10	Running one characterised vehicle in the attached garages of 16 Ottawa homes, chemical mass-balance modelling attributed 13% to 85% of the hydrocarbons measured indoors during cold starts, and 9% to 71% during hot soak, to emissions infiltrating from the garage. Contribution of vehicle emissions from an attached garage to residential indoor air pollution levels · J Air Waste Manag Assoc 2004 DOI 10.1080/10473289.2004.10470931 · PMID 15149044 · Abstract · read 2026-10-21
Persistence	1/10	unsourced input

Ratings are editorial. A study listed here supports the rating; it did not compute it. How the index is built

What this means for you

The chemical-hazard rating is what drives the score down. Exhaust in an attached garage carries carbon monoxide and benzene into the living space through the shared wall, and concentrations build quickly in an enclosed space. Backing out before starting removes the exposure completely and costs nothing.

Evidence strength: strong

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Lower-exposure choices

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