Residential, commercial or governmental houses have become the biotopes where we spend most of our time. We live, eat, exercise and work mostly indoor!
Since we exhale Carbon Dioxide (CO2), which can be dangerous in high concentrations and will affect our productivity level and decision making performance, good ventilation is required.
Open the windows please!
How hard can it be? We used to live or work in houses with natural draft or in less comfortable sun heated huts. As the energy crisis made us aware of the cost of burning fuel we started to dense walls, windows and doors. This in turn created new problems with moisture, sick building syndromes and bad air quality. As we crave for good air quality and a safe environment the next step was to work with controlled ventilation.
If you calculate the ventilation needed in a tight room, we can start with the need of one human being. Calculus being a normal 10 liters/second. Now you can estimate the number of occupants times the minimum rate required in your country (7l/s?).
But what do you do with a court room, a store or a cinema? If you calculate for the maximum amount of occupants, we will blow out the energy when the room is empty.
If we apply a sensor that measures CO2, the gas created by us and our machinery we can regulate the amount of air needed. With a pitot tube (same tube used on airplanes to measure speed by air flow) we can measure the amount of air provided.
A fan can produce a pressure in the air channels (i.e. 10 Pa) and the sensor regulates a damper.
A word of caution, it’s not the sensor that is the brain in the system. Our OEM customers apply logarithms and other means of control to make a system reliable and suitable for your application.
Now you might object that air quality is not only about CO2, an odorless gas that becomes dangerous at limits around 5000ppm and above. You are right, but research** has shown that an adequate airflow measured with CO2 takes other problems with it.
**Association of Ventilation Rates and CO2 Concentrations with Health and Other Responses in Commercial and Institutional Buildings
- O. A. SEPPA¨ NEN1, W. J. FISK2* AND M. J. MENDELL3