How can you make sure your indoor air is safe?


While scientists have long suspected a link between rising levels of CO2 in the outdoor environment and global warming, carbon dioxide can cause problems indoors too.


All India Institute of Hygiene & Public Health  has warned.

CO2 is also now recognized as being potentially toxic at low concentrations in consequence of cellular membrane effects and biochemical alterations such as increased PCO2 , increased concentration of bicarbonate ions , acidosis etc. Long term exposure to levels of CO2 between 0.5-1% may involve increased calcium deposition in body tissues including kidney associated with other altered tissue responses. In high concentrations, it may cause asphyxia , narcosis and unconsciousness .


A study by professional services firm KPMG found that indoor CO2 build-ups can cause headaches, eye problems, nasal symptoms and general feelings of fatigue.
Typical office levels are in the range of 600-800ppm (parts per million) – but a recent study by KPMG and Middlesex University conducted amongst 300 adults found that higher levels of CO2 could reduce concentration levels by as much as 30 percent. At levels above 1,500ppm, 79 percent of people reported feeling tired and above 2000ppm nearly two thirds of participants reported having no level of concentration. In addition, 97 percent of migraine sufferers reported symptoms at levels over 1000ppm.


KPMG’s health and well-being manager, Julie Bennett, said:
“If workers are feeling lethargic, apathetic or unable to concentrate in the office, it may not be the routines and stresses of their job, it could be that the levels of CO2 around them are too high.”


The ramifications can be considerable.
The cost of poor air quality (in terms of sick absence and time dealt dealing with the problem/complaints) in a large government office with 2500 occupants was £400,000 a year at 1990 prices, according to evidence submitted to a UK parliamentary Select Committee on the Environment*


Badly polluted air in Europe’s classrooms
Air quality and air pollution inside buildings is a subject of increasing concern for the public health authorities. It is recognised as a major factor influencing the respiratory health of both children and adults.Since children spend a large part of their time at school, it made sense to examine the possible respiratory implications of classroom air pollution.
More than two out of three schoolchildren in Europe are subjected to abnormally high levels of carbon dioxide and fine particulate matter (PM10). The alarm was raised at the annual congress of the European Respiratory Society (ERS) in Munich, where the results of a large international study, covering over 500 children aged nine and ten, were presented.


The quality of sleep

Scientists from the Delft University of Technology, The Netherlands investigated the environmental conditions of the occupied bedroom. They say carbon dioxide levels greater than 800 ppm indicates poor air quality in a bedroom and has many influences on health. They suggest that the quality of sleep is more important than the sleeping period.

What levels of CO2 are typical indoors?

The level of CO2 indoors depends upon:

  • the number of occupants
  • operation of combustion devices
  • the outdoor concentration
  • time of day the measurement is taken
  • the amount of outdoor air ventilating the area

The average human breathes:

out 18-23 liters of carbon dioxide per hour.
The fact that we breathe out such a large amount of carbon dioxide does not mean that it is safe or healthy for us to have high levels of carbon dioxide in our air.

The healthy bedrooms

The ventilation conditions in 35 bedrooms in family houses in La Coruna city (Spain) show, that CO2
levels are much higher than recommended. This was also found in monitored houses in Rotterdam, The
Netherlands. The maximum CO2 concentration in the bedroom varied between 2300 and 5480 ppm
(Rodriguez, ).


Values higher than 3000 ppm were reached when the bedroom had the door closed, even when there was only one person.
OTB Research Institute for Housing, Urban and Mobility Studies, Delft University of Technology, The Netherlands.

Experts recommend that the concentration of carbon dioxide in the air be below 1000-1200 ppm, or below 0.1-0.12%.