Radon, damp, carbon monoxide: what can be measured
Four real home risks go unnoticed: radon, wiring, damp, carbon monoxide; each can be checked, by a measurement or by a professional.
- Real risks
- Measurement
- Who to consult
What you can measure at home at a glance
What really threatens a home can be measured, and each risk has its own contact: you know what to check, and with whom.
- Guidelines read on
- October 20, 2026
- In your home
- My home in 6 questions
What you can measure at home
Radon
Radon is a natural, radioactive gas, with no odor or color, that rises from the ground and builds up in closed rooms: basement, ground floor, crawl space. Breathed for years, it raises the risk of lung cancer, even more among smokers. Nothing gives it away day to day. Look at your country’s official radon map if there is one, then measure: in the United States, EPA advises testing every home; in the United Kingdom, the measurement lasts three months.
The map should not be used to decide whether a home needs testing: no matter where you live, test your home. Fix the home at 4 pCi/L (150 Bq/m³) or more; consider fixing between 2 and 4 pCi/L (75 to 150 Bq/m³).
US Environmental Protection Agency : EPA Map of Radon ZonesRadon should be reduced in homes where the annual average is above 200 Bq/m³ (Action Level); 100 Bq/m³ is the Target Level. Measurements use two detectors, in a bedroom and a living room, over three months.
UKradon, UK Health Security Agency : Radon Action Level and Target LevelWHO recommends a national reference level of 100 Bq/m³, and no more than 300 Bq/m³ where 100 cannot be met. Radon is estimated to cause 3% to 14% of all lung cancers in a country.
World Health Organization : Radon
Who to consultYour national public health or radiation protection authority.
Electrical wiring
Wiring ages without showing it: what still works is not necessarily safe. Do not touch the panel yourself: a qualified electrician checks the panel, the grounding, and the protective devices, then tells you what must be redone. Rules differ from one country to another; in England, for example, rented homes must be checked at least every five years.
In England, landlords must have the electrics of rented homes checked at least every 5 years by a properly qualified person, and give tenants proof of it.
GOV.UK : Guide for landlords: electrical safety standards in the private rented sector
Who to consultA qualified electrician; your landlord if you rent.
Damp and mold
Black spots in a corner, peeling wallpaper, condensation running down the windows, a musty smell: damp settles quickly in a poorly ventilated home, and mold follows. The key is moisture control: dry any water damage quickly, ventilate every day, and if the marks come back, look for a leak or an infiltration and call a tradesperson.
The key to mold control is moisture control: clean up mold promptly and fix the water problem; dry water-damaged areas and items within 24 to 48 hours.
US Environmental Protection Agency : A Brief Guide to Mold, Moisture and Your HomeRemoving surface mould is not enough: the underlying causes, building defects, inadequate ventilation, and condensation, must be identified and tackled, or the mould comes back.
GOV.UK : Understanding and addressing the health risks of damp and mould in the home
Who to consultA plumber, roofer, or builder depending on the cause; your landlord if you rent.
Carbon monoxide
Invisible and odorless, carbon monoxide comes from incomplete combustion: a poorly maintained appliance, a blocked flue, a room without ventilation. If the detector sounds or several people feel unwell at the same time, you do not look for the cause: you get outside and call for help. Every year, a trained professional inspects the heating system, the flues, and the chimneys.
Have a trained professional inspect, clean, and tune up the central heating system (furnaces, flues, and chimneys) every year; keep gas appliances properly adjusted; open flues when fireplaces are in use; do not idle a car in the garage.
US Environmental Protection Agency : Carbon Monoxide’s Impact on Indoor Air QualityInstall battery-operated or battery back-up CO detectors near every sleeping area; check the batteries in spring and fall; replace the detector as the manufacturer says or every 5 years.
US Centers for Disease Control and Prevention : Carbon Monoxide Poisoning BasicsIf you suspect poisoning: stop using the appliance, go outside, and get medical advice; call 999 if someone finds it hard to breathe, is confused, or loses consciousness; do not go back in until you have had advice.
NHS : Carbon monoxide poisoning
Who to consultA heating technician or chimney sweep. Headaches or nausea in several people: stop the appliance, get outside, call 911 (United States) or 999 (United Kingdom).
Headaches or nausea for several people in the home: air it out, turn off appliances, get out, and call the emergency services (911 in the United States, 999 or 112 in the United Kingdom, 112 in Europe).
Official pointers, not a diagnosis: for any risk, the named authority is the reference.
What you can measure at home: your questions
How do you measure radon at home?
With a test kit or detectors analyzed by a laboratory. EPA advises testing every home in the United States and fixing it at 4 pCi/L (150 Bq/m³) or more. In the United Kingdom, UKHSA uses two detectors over three months and recommends reducing radon above 200 Bq/m³. Elsewhere, WHO recommends a reference level of 100 Bq/m³.
When should you have your wiring checked?
Before works, when you move into an older home, or if no one knows when it was last inspected. In England, landlords must have rented homes checked at least every five years by a properly qualified person. For any doubt in daily life, call a qualified electrician.
How do you remove mold from a wall?
Clean it up promptly, with a mask and gloves, without scraping it dry. Above all, fix the water problem, a leak, an infiltration, or a lack of ventilation: removing surface mold alone does not stop it from coming back.
What should you do if the carbon monoxide detector sounds?
Stop using the appliance if you can, get everyone outside, and call your emergency number: 911 in the United States, 999 in the United Kingdom, 112 in Europe. Go back in only once you have had advice. CDC advises a detector near every sleeping area, with batteries checked in spring and fall.
Official guidelines read on the original pages on October 20, 2026, reread at each quarterly review.
Read also
And in your home, what should you check?
Six questions about your home tell you which of these four risks concerns you, and who to turn to.
Check my home in 6 questions Free, no account · nothing is sent · no score