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Appendix F of the International Residential Code Adopted in Colorado Cities and Counties

The number of cities and counties in Colorado that are requiring passive radon mitigation systems (Appendix F in the local building code) in all new homes continues to grow. Approximately half the homes in Colorado have levels of radon that exceed the USEPA recommended action level of 4 pCi/L. Because of the high potential for excessive radon to be present in homes, radon resistant new construction is an important issue. In an effort to assure passive radon mitigation systems are built into new homes, numerous Colorado cities and counties have adopted building code requirements. As of May 25, 2018, cities that have adopted Appendix F total 24. Counties that have adopted Appendix total 13. The following is the listing of cities and counties.

• Aspen
• Breckenridge
• Cedaredge
• Crested Butte
• Dillon
• Durango
• Frisco
• Ft Collins
• Golden
• Gunnison
• Lake Lakewood
• LaVeta
• Longmont Mount
• Crested Butte
• Orchard City
• Pagosa Springs
• Ridgway
• Silverthorne
• Snowmass Village
• Sterling
• Superior
• Trinidad
• Vail
• Walsenburg

• Archuleta County
• Boulder County
• Eagle County
• Gunnison County
• Huerfano County
• Jefferson County
• La Plata County
• Las Animas County
• Logan County
• Montrose County
• Pitkin County
• San Miguel County
• Summit County

Multi-family Radon-Resistant New Construction required: Ft Collins

For more information about radon in Colorado, contact:

Chrystine Kelley
Colorado Department of Public Health & Environment
Radon Program Manager
Telephone: 303.692.3442