carbon dioxide

In some buildings in Canada ventilation systems are being operated with the outside air supply dampers completely closed during winter to reduce ventilation and hence conserve energy. Reports measurements of the carbon dioxide concentrations in the classrooms of a small elementary school, when the outside air-supply damper was closed, to assess whether ventilation was adequate. Concentrations were found to be well below the maximum accepted occupational standard of 0.5% and air infiltration gave an adequate fresh air supply.

The ventilation rate and energy consumption of one of the ECRC test houses was monitored continuously during one heating season, with one bedroom window open by various amounts. Results show that a very small window opening is sufficient to satisfy ventilation requirements most of the time. 

Describes tests in Exeter University library of method of determining ventilation rate by measuring the amount that the atmospheric carbon dioxide concentration in an occupied space is raised above the outside ambient level. Compares rate obtained with that expected from the fan rating. Demonstrates that in addition to the ventilation rate, the average rate of production of carbon dioxide produced by the occupants could in principle have been estimated from the data.

Treats investigations in office building where 1) flow rates of supply air, return air and ventilation between main office area and adjacent rooms were measured with an anemometer. Return air rates remained constant but ventilation rates varied widely during measurement periods. 2) CO2 was used as tracer gas to determine ventilation rates in offices. Calculates alterations in gas concentrations in rooms adjacent to stairwell and changes in outdoor air concentrations. During air conditioning, ventilation rates in the room were 4-5 room air changer per hour.

Reports the results of three programmes of measurements of ventilation carried out in one-family houses, which in most cases were of the 'council house' type. The first programme measured ventilation rates using tracer gasin two houses room by room. Wind speed and direction were recorded but no general relation between ventilation and wind was found. The second measured ventilation rate in individual rooms in a house under six different wind conditions. The third measured ventilation rates in three identical homes.

Treats importance of keeping uncontrolled ventilation to a minimum in buildings equipped with balanced ventilation. Provides theoretical and experimental description of leakage of air past windows. Includes comparison between standards of different countries. Discusses effect on building ventilation of variations of wind and outdoor temperature. Considers in conclusion measurement of air flows between rooms in a building. Describes development of tracer gas method based on computer-assisted evaluation.

Describes technique for measuring the volume of air leaving a house through the loft. Two tracer gases are used; nitrous oxide is released in the house and carbon dioxide in the loft. The mean concentration of N2O in the loft gives the volume of house air infiltrating the loft: and the mean concentration of CO2 gives the ventilation rate of the loft itself.< Gives two examples of the use of this technique and gives loft ventilation rate as a function of wind speed for one house.

Natural ventilation of inhabited rooms is studied with regard to its dependence on wind velocity and temperature difference between the interior of buildings and outside air. On the basis of simultaneous aerosol and carbon dioxide measurements an attempt has been made to separate the two components of air exchange: ventilation through walls and ventilation through clefts and chinks.

Describes method for measuring the direction and volume of air flows in a building with several rooms. The method uses carbon dioxide as a tracer gas produced from dry ice in each room. Over a period of 2-3 hours the concentration of gas in each room is measured every ten minutes. Gives equations for calculating air flows between rooms and some results of tests made on a flat.

Reports investigation of the relative effectiveness of wall gratings and flues as means of naturally ventilating unheated closed rooms. Ventilation rates of several rooms were measured using carbon dioxide as tracer gas and wind speed and direction were recorded. Presents results and finds for the flue, ventilation increased with wind speed irrespective of direction. For grating, ventilation rate increases slowly with size of grating and is dependent on both wind speed and direction. Concludes flue with base opening of 15 sq.ins. is as efficacious as grating having 50 sq.ins.