How dangerous is CO2 in the home? Chris looks into the importance of looking after your appliances

25 Sep 2014

Last week we looked at Carbon Dioxide from an industry point of view, so this week I thought I’d highlight the dangers of this gas from a domestic side.

What is Carbon dioxide?

Carbon dioxide (CO2) is a gas that the human body produces naturally. Everyone is exposed, to some degree, to this gas every day. It occurs naturally in the Earth’s atmosphere as part of animal metabolism, plant photosynthesis, decomposition, and combustion. The gas is colourless, odourless, tasteless, non-combustible, is soluble in water and makes up slightly less than 0.5% of our atmosphere. CO2 is classed as a ‘greenhouse gas’ and increasing CO2 is debated to be one of the main causes of global warming.

How dangerous is it?

Carbon dioxide is an often-overlooked killer. Although the air always contains an amount of CO2 that we breathe in and out every day, and is perfectly harmless in normal conditions, a build-up of CO2 in the air will cause humans and animals to absorb less oxygen into their bloodstream, instead increasing the levels of CO2 in the bloodstream in its place. This will slowly starve the body of oxygen, leading to brain damage and even death.

Carbon dioxide in the home

Carbon dioxide accumulation inside the home is normally related to the number of occupants, and concentration of the gas is usually highest where homeowners spend most of their time. Appliances in the home can create extra CO2 in the atmosphere, so making sure that they are all serviced and functioning correctly is essential.

For example, combustion produces CO2, so boilers are fitted with a special flue that directs the gas up and out of the home without it leaking into the household air. It is rare, but sometimes these flues can become damaged and allow CO2 to seep into the house, causing a higher ratio of CO2 in the air, which could be dangerous. To prevent this, it is strongly advised that you service your boiler thoroughly by a qualified Gas Safe registered engineer, who will check for any leaks or damage to your boiler system. Keeping your home well ventilated is key to preventing a build-up of CO2.

Knowing when levels are too high

Since increasing levels of CO2 encourage plant growth, an unusual flowering or blooming of household plants may indicate an overabundance of carbon dioxide. Also, carbon dioxide by nature is 1.5 times heavier than air, and therefore tends to ’pool’ in low areas such as basements.

Below you’ll see levels measured and the affects to watch out for:

% AirParts per millionAffects
0.4250-350Normal background concentration in outdoor ambient air
0.1350-1,000Concentrations typical of occupied indoor spaces with good air exchange
0.21,000-2,000Complaints of drowsiness and poor air
0.52,000-5,000Headaches, sleepiness and stagnant, stale, stuffy air. Poor concentration, loss of attention, increased heart rate and slight nausea may also be present
0.55,000Workplace exposure limit (8-hour TWA)
4>40,000Exposure may lead to serious oxygen deprivation resulting in permanent brain damage, coma or even death


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