Vents

Vents are important elements that help keep air circulating to reduce moisture buildup, let hot air out, and the screen helps keep rodents out.  Vents with ¼ inch openings have large enough gaps to allow embers to penetrate the building, and given their size, smolder for a while. If combustible items are located inside the vent, smoldering embers may ignite those items. When assessing the vents on your home, think about:

• Is the mesh screen larger or equal to 1/4” (6.4 mm)? Large embers can easily pass through them.
• Is there any vegetation or combustible material within 5ft (1.5m) from the vents? If nearby materials burn, they can potentially expose the vents to flames or embers.
• Does the mesh screen have debris and/or paint clogging it? If so, these materials could burn if they came in contact with flames.

Diagram illustrating the different locations of vents around the home.

There are many different locations for vents around the home. Below is a list of common household vents.

 

Vent Type	Description	Vulnerabilities
Dryer and Garage Vents	Dryer vents connects a clothes dryer to the exterior of a building, allowing heat, moisture, and lint to escape safely. Garage vents are openings designed to facilitate air exchange in a garage.	Lint or other debris in the vicinity of these vents (both inside and outside) could easily ignite in contact with embers.
Foundation Vents	These vents are usually on the lower section of exterior walls.	Due to their location, these vents may be exposed to more embers and flames if materials nearby ignite. The area in proximity of the vents should be free from vegetation and other combustible materials.
Gable Vents	This type of vent serves both as an intake and exhaust vent. It is installed on opposed sides of the home for cross-ventilation.	Traditional vents could expose the attic to ember ignition.
Ridge Vents	Ridge vents are specialized exhaust vents installed along the peak of a sloped roof to allow hot, humid air to escape the attic.	Leaves and debris usually do not accumulate by the ridge of the roof. However, traditional vents have plastic components that could ignite or melt when exposed to flames or embers.
Roof Vents	Roof vents are designed to manage attic temperature and moisture by allowing air to circulate.	These vents are very vulnerable to ember entry and could directly expose the attic, especially if they face upcoming wind.
Soffit Vents	Usually located under the eave of the roof.	Vegetation or other combustible materials near the exterior walls could directly expose these vents.

 

How Can You Protect Your Vents?

The first step is to locate all vents on your property and determine whether they need immediate attention. There are a number of retrofitting recommendations to protect your vents, including:

• Replacing your vents with fire-resistant vents approved by the California Office of the State Fire Marshall. There are several California Office of the State Fire Marshal-approved flame- and ember-resistant vents. These vents meet the standards in the California Building Code. Some of these vents are shown below in alphabetical order:

Brandguard Vents

These vents use a baffle design to deviate the embers path.

Embers Out

These vents have multiple internal layers of louvers that block embers.

O'Hagin Vents

Low profile through-roof vents, approved for over eave applications.

Vulcan Vents

They use screenings on the front and back of a honeycomb matrix. This matrix is coated with an intumescent paint that swells when exposed to heat.

• Retrofit your existing vents with metal mesh (1/8-inch or 1/16-inch screening). For existing vents with 1/4-inch screens, you can add a second layer of screen of a smaller mesh size (1/8-inch or 1/16-inch) to cover the existing ¼-inch mesh.

  • Install the finer mesh screens from the inside or outside (whichever is easier) to help keep embers out. 
• Regardless of vent type or location on the home, all vents should be checked regularly. Vegetation and other combustible materials should be kept away from vents to reduce likelihood of exposure to embers and flames.
• If you were not able to replace or retrofit your vents before a fire approaches your area, you can use plywood or metal tape to temporarily cover the vents before evacuation if time permits.

California Regulations

According to Chapter 7A of the California Building Code;

• Screen mesh for roof vents should be made with corrosion-resistant and non-combustible materials, with openings between 1/16 and 1/8" (1.6 and 3.2 mm).
• Chapter 7A prohibits the use of vents in eaves unless they have proven to resist the intrusion of embers and flames.

Products and assemblies that have complied with Chapter 7A can be found in the WUI Product Handbook. 

Additional Resources

Check out these vent-related wildfire preparedness resources from Fire Network Members and our colleagues!

• Vulnerability of Vents to Wind-Blown Embers report by Stephen Quarles (Insurance Institute for Business and Home Safety, 2017).
• Video from the Insurance Institute for Business and Home Safety (IBHS) showing wildfire vent testing at the IBHS Research Center