Radon and mold testing cost in Washington (2026):
tests, mitigation prices and when to act
HOW MUCH DOES RADON AND MOLD TESTING COST?
Angi puts professional radon testing at $145 to $714 (average $420), while do-it-yourself radon kits run about $10 to $60. A mold inspection averages $671, usually $302 to $1,046. If radon is 4 pCi/L or higher, the Washington State Department of Health recommends reducing it; Angi puts radon mitigation in Seattle at $943 to $1,852, with an average of $1,397.
Radon testing cost
| Test | Reported cost |
|---|---|
| Short-term DIY kit | $10–$40 |
| Long-term DIY kit | $25–$60 |
| Digital / continuous monitor | $100–$250 |
| Professional testing | $150–$700 |
| Average, all testing | $420 (typical $145–$714) |
- Why test. The Washington State Department of Health says radon is "the leading cause of lung cancer among non-smokers," and that "the only way to know your radon levels is to test."
- The action level. DOH points to the EPA action level of 4 picocuries per liter (4 pCi/L) of indoor air; above that, take steps to reduce it.
- DIY kits are sold at home improvement stores and online; you mail the kit to a lab for results (DOH).
Radon mitigation cost in Seattle
| Seattle (Angi) | Reported cost |
|---|---|
| Typical range | $943–$1,852 |
| Average | $1,397 |
| Active soil depressurization (fan system) | $1,000–$3,000 |
| Passive depressurization | $500–$2,500 |
| 1,500 sq ft home / 3,000 sq ft home | $900–$1,650 / $1,800–$3,300 |
DOH says many fixes are inexpensive and simple, such as installing an exhaust fan, and recommends a certified radon mitigation company if levels are elevated. Washington sales tax applies to the contract, labor included: see sales tax on home repairs.
Mold inspection and testing cost
| Test | Reported cost |
|---|---|
| HVAC test | $50–$75 |
| Swab (surface) test | $200–$300 |
| Air test | $250–$350 (up to $700 for extensive testing) |
| Home under 4,000 sq ft | $300–$400 |
| Average inspection | $671 (typical $302–$1,046) |
Mold usually follows moisture. If testing finds a problem in a crawl space or basement, the fix is often about water: see crawl space encapsulation cost and basement waterproofing cost.
Buying a home
- Radon and mold tests are usually separate from a standard home inspection; ask your inspector which add-ons they offer. See home inspection cost in Washington.
- Older homes may also need lead paint or asbestos checks before renovation: see lead paint rules and asbestos testing and removal.
Frequently asked questions
How much does radon testing cost?
Angi puts professional radon testing at $145 to $714, with an average of $420. Do-it-yourself kits run about $10 to $40 for a short-term test and $25 to $60 for a long-term test.
How much does radon mitigation cost in Seattle?
Angi puts radon mitigation in Seattle at $943 to $1,852, with an average of $1,397 (February 2026). Larger homes cost more: $1,800 to $3,300 for 3,000 sq ft.
What radon level is dangerous?
The Washington State Department of Health points to the EPA action level of 4 pCi/L of indoor air; above that, it recommends steps to reduce radon.
How much does a mold inspection cost?
Angi puts the average mold inspection at $671, usually $302 to $1,046. An air test runs $250 to $350 and a swab test $200 to $300.
Is radon testing part of a home inspection?
Usually it's an add-on. Angi's home inspection guide lists radon among specialized inspections, at about $250. Ask the inspector before you book.
About these prices. The ranges are published estimates from the sources below, as of the dates shown. Material costs, labor rates, tariffs and inflation can change prices after those dates, and your home may differ. Use them to plan a budget, then get written quotes from licensed contractors.
Sources
- Washington State Department of Health — Radon in Washington, DOH 323-002 (January 2022)
- Angi — Radon testing cost
- Angi — Radon mitigation cost in Seattle, WA (February 10, 2026)
- Angi — Mold inspection cost
- Angi — Home inspection cost (2025 data)
All sources accessed November 10, 2026.
This guide summarizes published cost estimates and Washington State Department of Health information. It is not medical advice. For radon questions, call the DOH Radon Hotline at 360-236-3200. See our disclosure and disclaimer.