Select and install a chimney cap/spark arrestor that satisfies mesh-size, corrosion-resistance, and wildfire-zone requirements

Steps

1. Determine whether the property is in a designated wildfire-risk/wildland-urban-interface (WUI) area under the locally adopted fire code, since additional spark arrestor requirements typically apply there
2. Confirm the base mesh-opening requirement with the local fire/building code — many California-derived codes require openings that do not pass a 1/2-inch sphere while remaining open enough to pass a 3/8-inch sphere
3. Select a cap/arrestor mesh gauge that satisfies that opening range in practice; 5/8-inch mesh screen is commonly used in California WUI applications because its actual opening is small enough to meet the sub-1/2-inch sphere requirement
4. Confirm the screen material has heat/corrosion resistance equivalent to the code-specified minimum (commonly referenced as roughly 19-gauge galvanized steel or 24-gauge stainless steel in California-derived code language) — verify the exact figures against the currently adopted local fire code
5. Size and install the cap per the chimney/liner manufacturer's listing so the cap does not restrict draft or violate the liner's listed termination requirements
6. Check and document any HOA architectural requirements separately, since HOA covenants may impose additional appearance or material restrictions beyond the fire code minimum