The short version
- Never tested for radon? Start with a $20 kit. Test kits ↓
- Tested high, mitigated, or want ongoing numbers? Get a continuous monitor. Monitors ↓
- CO alarms older than 7 years, or missing on a floor? Replace them before the furnace runs full-time. CO detectors ↓
Prime Big Deal Days pricing is for Prime members only. Not a member? Start a free Prime trial before the sale.
Radon monitors
Indoor radon usually runs highest in winter, when windows stay shut and the house draws soil gas up through the foundation. A continuous monitor shows you what your levels actually do across the season, which a one-time test can't. Full comparison: best radon detectors.
Airthings Corentium Home
Best value for most homes. Proven accuracy, years on AAA batteries, no app or subscription. Full review →
RadonEye RD200
One of the fastest-responding consumer monitors, with a first reading in about an hour. Good for checking a mitigation system. Full review →
Airthings Wave Plus
Radon plus CO₂, VOCs, humidity, and temperature, with app history. Our pick if you want whole-home air data. Wave Plus vs. Corentium →
Airthings View Plus
The smart-home option: Wi-Fi, on-device display, remote alerts. Worth it for rentals and second homes. View Plus vs. Wave Plus →
Radon test kits
Short-term radon tests are supposed to run under closed-house conditions, which makes heating season the natural time to test. A $20 kit is still the right first step if you've never tested. All five kits compared.
First Alert RD1
Best first screening test: simple charcoal kit, long track record, under $20 before lab fee. Kit comparison →
Leaping Lynx (Alpha Energy Labs)
Lab fee included, NRPP-certified results in 3–5 days. The one to use when you need documentation. Kit comparison →
Carbon monoxide detectors
Most accidental CO poisonings happen in the colder months, once furnaces, space heaters, and generators start running. Fire Prevention Week (Oct 4–10) is a good reminder to check the manufacture date on every alarm; CO sensors wear out at 7–10 years. All CO picks compared.
Kidde 10-Year Sealed Battery (digital)
Best overall. Shows CO in ppm with peak memory, and no battery changes for a decade. CO detector guide →
First Alert CO400 (6-pack)
Cheapest way to put an alarm on every level and outside every bedroom at once. Where to put them →
First Alert CO410
Digital ppm readout for less. Uses replaceable batteries. CO detector guide →
Kidde Plug-In with Battery Backup
For hallways and basements with an outlet. The backup keeps it working during outages, when generator CO risk is highest. CO detector guide →
Water filters
Reverse osmosis is the most reliable home option for PFAS. Activated carbon removes only part of it, and most standard pitcher filters remove little. See best PFAS water filters and do Brita filters remove PFAS?
iSpring RCC7AK 6-Stage RO
Best overall under-sink RO, with remineralization for better taste. DIY install in an afternoon. RO comparison →
Waterdrop G3P600 Tankless RO
Tankless and compact, with much less wastewater than tank systems. RO comparison →
ZeroWater 52-Cup Dispenser
The no-install option. Owners consistently report 000 TDS readings after filtering, and a meter is included. Full review →
Filters are the real cost. If you own a ZeroWater, the replacement filter packs are worth setting up on Subscribe & Save. You get a recurring discount on a part you'll buy every few months anyway, and you don't have to remember to reorder.
Mold test kits
Closed-up, humid homes in fall are when musty smells show up. A DIY kit tells you whether mold is growing; it won't tell you where it's coming from. All mold kits compared.
Evviva Sciences Mold Test Kit
Best overall: 10 dishes for air, surface, and HVAC testing across several rooms. Mold kit guide →
A sale is a good reason to buy, not a reason to skip testing
A detector only helps if it's in the right place and you act on what it tells you. If a radon result comes back at or above the EPA's 4 pCi/L action level, read our what to do after a radon test guide and what mitigation costs. For your area's risk, look up your city hazard report.