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Measurement · Air qualityCO

Carbon monoxide

Carbon monoxide is a colourless, odourless, toxic gas produced by incomplete combustion. It is dangerous because it is undetectable by people and interferes with the blood’s ability to carry oxygen. Continuous monitoring is a direct safety measure wherever fuel is burned.

< 9 ppm
Healthy 8-hour exposure target
Electrochem
Dedicated electrochemical sensor
60s
Reading interval, logged continuously
Boiler Room · Basement
safe
1ppm
Safe · safe
050+ ppm
Last 24 hourswithin target
00:0008:0016:00now
Why measure it

A safety parameter, not just a comfort one.

Unlike most readings here, CO can be acutely dangerous — which is exactly why it must be measured rather than assumed.

Acutely toxic

CO binds to haemoglobin in place of oxygen. High levels cause headaches, confusion, collapse and, untreated, can be fatal.

Undetectable

It has no colour or smell, so people cannot sense it. A sensor is the only reliable warning before symptoms appear.

Faulty combustion

Blocked flues, poorly maintained boilers and unflued heaters are classic causes — monitoring catches them early.

Alerting

Continuous CO data drives instant alerts, turning a silent hazard into an actionable warning.

How to read it

Should normally be near zero.

In a healthy space CO sits close to zero. Any sustained reading is a prompt to investigate combustion; high levels demand immediate action.

1 ppm
0 ppm50+ ppm
0–9
Safe
Normal background. No combustion problem indicated.
9–25
Elevated
Above the healthy target. Check appliances and ventilation.
25–50
High
Unsafe for continued occupancy. Ventilate and find the source.
50+
Dangerous
Dangerous. Evacuate, ventilate and shut down combustion sources.
Where it comes from

Wherever combustion goes wrong.

CO comes from incomplete burning of fuel — so its sources are the same appliances and equipment that should be burning cleanly.

01

Heating appliances

Boilers, furnaces and unflued heaters produce CO when burning incompletely or when flues are blocked.

02

Gas cooking

Gas hobs and ovens emit some CO, more so when poorly adjusted or used without ventilation.

03

Engines & generators

Vehicles in adjacent garages and fuel-powered generators are major, dangerous sources if exhaust enters the building.

04

Blocked ventilation

Anything that stops combustion gases venting safely — blocked flues, negative pressure — can let CO build up indoors.

What good looks like
< 9 ppm

Keep CO below 9 ppm over 8 hours; any sustained indoor reading warrants investigation of combustion sources.

WHO 2021WELL v2EN 50291
Measured by your monitors

Carbon monoxide is measured on MICA WELL — available on the Premium tier for total air-quality coverage.

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