Ventilation is a set of actions and techniques used to arrange air exchange and to provide a specific air medium condition in the premises and in working places. Ventilation maintains desirable indoor climatic parameters in compliance with set hygienic norms and technology requirements.
We are surrounded with air and breathe in and out 20 000 litres of air every day. How much healthy is the air we breath in? There is a range of aspects to determine air quality.
– Oxygen and carbon dioxide concentration in the air. Oxygen decrease and carbon dioxide cause stuffiness in the premises.
– Content of harmful substances and dust in the air. High content of dust, tobacco smoke and other substances in the air are harmful for the human organism and can cause various lung and skin diseases.
– Odours. Bad smell causes discomfort and irritates.
– Air humidity. Too high or low humidity makes us feel uncomfortable and even may provoke acute disease attacks for sick people. Air humidity is important also for inner climate. For instance, doors, window frames, furniture may shrink because of too low humidity in winter and get swollen in humid environments, e.g. in swimming-pools, bathrooms.
– Air temperature. The comfortable indoor temperature is within 21-23 °C. Higher or lower temperatures influence physical and mental activity and health condition.
– Air motion. Increased air motion in the premises causes drafts and low air motion causes air blanketing. Any of these factors influence our well-being.
Properly arranged ventilation system in the only solution in this situation. It provides supply of filtered air in summer and supply of filtered and warmed up air in winter as well as extract stale air removal from the premises,
Any ventilation system must include synchronous fresh air supply and extract air exhaust thus ensuring the ideal air balance in the room. In case of poor or insufficient air intake from outside the oxygen content decreases, humidity and dustiness level increase. If exhaust ventilation is not provided or it is not efficient, polluted air, smells, humidity and harmful substances are not removed. One more important factor for properly arranged ventilation system is joint operation of supply and exhaust air vents. If indoor ventilation is provided by air exhaust only, e.g. by an extract bathroom fan, and the only possible air supply source is the gaps in windows, doors and construction elements. This uncontrollable air supply results in dust ingress, smells and draughts. Ventilation grilles in the bathroom doors, wall or window vents, open windows are the only natural supply air sources that may compensate for air extraction. However mechanical ventilation is the only solution to provide central air supply in the rooms.
Calculation of air exchange according to air exchange rate:
Ventilation air volume is determined for each premises separately considering concentration of harmful substances. Alternatively, ventilation air volume calculated be set according to the research results. If the nature and concentration of harmful substances is not possible to determine, air exchanged is calculated as following:
L = V prem. * Ach [m3/h],
Where V prem. – premise volume [m3];
Ach – minimum air exchange per hour, refer air exchange table.
Air supply and exhaust ventilation in the modern office can be arranged as follows. Air handling MPA unit, exhaust fan complying with MPA unit characteristics, intake and exhaust man air ducts are mounted in the hall behind the suspended ceiling. The branchings are laid into the office premises and air distribution units. Intake air from outside flows through the external grille, is filtered in the air handling units, heated to the required temperature and supplied to the office rooms through the branch duct system. Exhaust air is extracted outside through the external grille by means of the exhaust fan.
Thus the office has the permanent fresh air supply, controllable air exchange, no draughts when opened windows, no dust and no noise.