What mesh size is recommended for ember-resistant vents to reduce ember intrusion?

• A. 1/8 inch
• B. 1/4 inch
• C. 3/16 inch
• D. 1/2 inch

Answer: (A)

Ember-resistant vents reduce ember intrusion by limiting the size of openings that embers can try to pass through during a wildfire. The smaller the openings, the less likely embers are to penetrate into attic or crawlspace spaces. A mesh size of 1/8 inch (about 3 mm) is the most effective commonly used option because it blocks a wide range of ember sizes while still allowing adequate airflow for ventilation. Larger mesh sizes—3/16 inch, 1/4 inch, or 1/2 inch—create bigger gaps that embers can slip through, offering substantially less protection. Therefore, 1/8 inch mesh is the recommended choice to reduce ember intrusion.