What does our office breathe with?
Every one of us inhales at least 500 litres of air per one hour (and even eight times more during physical effort), so it is not indifferent to what quality of air we breathe in. Considering the fact the we spend most of the time – both at work and after work – in overheated, badly ventilated and closed rooms (with particles of strong allergens: saprophytes, fungal and mould spores, human and animal epidermis, animal hair), the issue becomes especially important.
According to scientists, the most important condition for human well-being is the appropriate quality of the surrounding air (the content of oxygen counts) and the thermal comfort.
The air quality is undoubtedly influenced by good ventilation, and good thermal comfort is provided by a properly designed heating system in winter and an air-conditioning system in summer.
Appropriate ventilation of rooms is necessary both for health, safety, and comfort of users as well as for functioning of equipment.It would be an ideal solution to provide for a possibility of natural ventilation; if it is not possible, then ventilation must be supported mechanically.
Ventilation means removal of foul air from rooms and supply of fresh air. Natural ventilation takes place due to difference between air temperature outside and inside of the given building.
On the other hand, mechanical ventilation means supporting the exchange of air through forcing of air flow (fans, ventilators).
Air counted in streams
Every room requires exchange of air.
The requirements for various rooms (depending on their destination and equipment) are specified as streams of air (amount of exchange processes).
A stream of air is an amount, which must be removed from the given room within one hour. A stream of removed air corresponds to a stream of supplied air - this is why an “exchange” of air is often referred to.
According to the norm PN-83/B-03430/Az3:2000 (Ventilation in dwelling houses of collective residence and public utility - Requirements), the stream of air for buildings of public utility depends on the number of persons staying in the building and is specified as:
- 20 m3/h per person staying in the building,
- 30 m3/h per person staying in the building, if smoking is allowed,
- 15 m3/h per child (nurseries and kindergartens).
Natural ventilation
Natural ventilation, called also gravitational ventilation, is the most frequently and commonly used type of ventilation in Poland. It functions due to use of the difference between air density outside and inside of the given building. In a natural way, the air penetrates through leakages in the housing of the building into its interior, and having been blended with impurities and heated, it gets out of the building through ventilating ducts.This process is possible only when the building intakes an appropriate amount of air, which ensures the required intensity of removal of impurities and a proper chimney draught.Inflow of air to the building increases with the wind.Functioning of natural ventilation depends also on the time of day, the time of year and on weather conditions. Thus, natural ventilation does not function all the time, and it happens many times that the system does not function at all.
Natural ventilation depends on weather conditions – if the difference between air temperature outside and inside of the building is substantial, the ventilation functions efficiently. In summer, when temperatures inside and outside of the building are comparable, the ventilation does not work or warm air is flowing into the building. The worst situation occurs in spring and autumn, when the weather conditions are not favourable for ventilation.
Airtight buildings do not have a positive impact on functioning of natural ventilation.
Buildings constructed at present are more and more insulated. Thus, uncontrolled flow of air through walls and windows is effectively limited. It is necessary with respect to heat losses, but it also involves a limitation of ventilation intensity in the rooms. This way, the quality of the air inside is decreased. It leads to occurrence of the sick building syndrome. The low quality of air results in an increase of its relative humidity. The moisture, dropping out on the inside area of window panels and cool wall areas, creates good conditions for development of fungi and mould.
Mechanical ventilation
Natural ventilation is limited in its scope of functioning. The pressure difference provided by temperature differences, or under the influence of a breeze is often not sufficient. In such a case, it is necessary to apply mechanical ventilation.
In mechanical ventilation, exchange of air is independent from any weather conditions. The forced airflow is achieved through use of one or more fans. Mechanical ventilation can be used in many various forms, depending on the method for exchange of air, the direction of air circulation in relation to the room ventilated or differences of pressure inside and outside of the room.
There are three basic types of ventilation:
· Mechanical supply ventilation – in systems of supply ventilation, the air is forced into rooms through fans, and the outflow takes place automatically through leakages. The air forced in by the fan provides for an overpressure, due to which the air flows through holes out of the room at the same time.
· Mechanical exhaust ventilation – the air is removed from rooms through exhaust fans, and the inflow takes place automatically through leakages or special holes. Due to intensive removal of air, an overpressure is produced, resulting in inflow of air from adjacent rooms.
· Supply and exhaust ventilation – the most appropriate ventilation method. The system makes it possible to meet completely the requirements for ventilation as an efficient flow, production of negative pressure or overpressure in rooms. The supply and exhaust installation requires application of two systems. The air flows into rooms through a system of intake ventilators, is distributed in the whole dwelling through ventilating ducts, and then gets out through uptake ventilators. The circulation of air is forced by fans. Intake ventilators in form of grids, slots, or strips are installed in window or door openings.
General ventilation provides for an even exchange of air in all rooms, and local ventilation prevents all impurities in the place where they are created.
Local ventilation includes:
· local draughts – used for removal of impurities directly in the place where they are created
· local intakes, used for creation of conditions in a specific place, differing from the conditions of the whole room
· air curtains, used for protection of rooms against penetration of cold air (in winter) or hot air (in summer) from outside through frequently opened gates and doors in industrial buildings or public utility buildings
Too tight windows
Airtight windows decrease the quality of the air inside the building.
Due to this feature, producers started looking for new solutions some time ago. At first, they began to remove pieces of gaskets in the upper part of the window, and then they introduced fittings, which made it possible to unseal windows and provide for micro ventilation. Removing of pieces of gaskets did not bring much effect. Use of micro ventilation turned out to be more effective. However, this solution is efficient only then, when users make an aware use of it. It is a common case that customers who buy modern windows do not remember about the unsealing option or even do not want to use this possibility.
In such a situation, one should use special air intakes in order to ensure effectively appropriate airflow into the building. These devices can be installed in a window or on an external wall of the building, and will ensure a specific airflow. Because they are located near the window, the air received into the room is automatically heated. The volume of the flow can be regulated manually or automatically, depending on the type of the device.
According to the requirements of the norm PN-83/B-03430, airflow of 20 to 50 m3/h should be provided in case of natural ventilation, and of 15 to 30 m3/h in case of mechanical ventilation.
Today, when airtight PVC windows or wooden windows with gaskets are commonly used, the inflow of air needed for ventilation is limited. There is a risk of repeated situation of the 70’s of the 20th century, when introduction of energy-saving windows in west European countries resulted in lack of ventilation. Consequently, it led to an increase of humidity in rooms and development of mould fungi.
During the works on the revision of the norm PN-91/B-02020 „Thermal protection of buildings”, the air infiltration rate was limited. According to the document, the rate should lie below 1.0, but above 0.5 m3. In wooden windows without gaskets, the infiltration rate amounts to approx. 1.0. However, in case of use of gaskets, the infiltration rate falls to approx. 0.1. This applies both to PVC and to wooden windows.
In order to achieve an appropriate level of infiltration, one should unseal windows, cutting out a piece of the rebate gasket or replacing it with a flat gasket in a specific length. A window unsealed with this method meets the requirements of legal norms, making it possible to achieve an infiltration rate of 0.5 - 1.0 m3.Such an unsealed window provides for penetration of a safe amount of air, but it does not meet hygienic requirements. In order to meet both the requirements, users should open the sashes or use intake ventilators in the window frame.
Intake ventilators are placed in the upper part of the window (header, rebate, or sash), a roller shade cassette above the window or in the wall next to the window. Due to the accessibility of the location, they often have the form of strips, which – in consideration of their function – are called ventilation strips.
Thermal comfort
One of the tasks of a properly construed building and its equipment is to ensure thermal comfort for its users.Thermal comfort means such values of air parameters (temperature, relative humidity, circulation speed) which provide a sense of comfort to persons staying in a heated and ventilated room. The basic parameters are: temperature and relative humidity of air.
Relative humidity means a ratio of actual content of moisture in the air to the maximum content for the given temperature (the state of saturation). This value is expressed as a percentage and shows the amount of moisture contained in the air for the given temperature.
Thermal comfort is to some extent a question of subjective perception. On the other hand, there are ranges of temperature and humidity specified which are not only perceived as pleasant by most people, but is also favourable for a good mental and physical shape. These values change, depending on the time of the year, and are related to differences of temperatures between the room and the outside environment.
According to the norm PN-83/B-03430 (including the Az3 change), the values of the basic parameters: temperature and humidity) amount to:
| time of the year | temperature in °C | relative humidity % |
| summer | 23-25 (± 1.5°C) | 50%, deviation of 10% |
| winter | 21-22 (± 1-1.5°C) | 45%, deviation of 10% |
It should be noted here that temperature distribution is important for our well-being and good shape as well: at the height of the head, lower temperatures (18 - 20°) are more favourable, and at the height of the feet (on the floor), the temperature should amount to 24-26°. At the same time, it should not exceed the following values:
- 27°C in work rooms where people work in standing position
- 29°C in areas of permanent stay of people (residence and office rooms)
- 33°C in kitchens and bathrooms.
Air-conditioning
The task of air-conditions systems is to maintain a proper purity, temperature and humidity of air in closed rooms through appropriate devices. The air in the room can be cooled or heated up, depending on the function set on the control panel of the air-conditioner.
Air-conditioning systems improve the microclimate in air-conditioned rooms as well, due to which they enhance the working comfort.
Air-conditioning systems provide for a regulation of:
- air purity through filtration of air
- air temperature in summer and winter
- air velocity field
- relative humidity of air
In air-conditioning systems with cooling functions, excessive heat is absorbed by the refrigerant circulating in the system. The cooling process takes place in the following way:
- the air-conditioner draws in warm air from the environment
- the warm air is forced into the cold cooler
- the process of cooling and dehumidifying of air takes place
- cold air is blown into the room
An automatically repeated cycle allows for maintenance of a required and appropriate temperature in the room.
Due to the use of a heat pump system, air-conditioners can perform the heating function as well. The refrigerant circulating in the system receives heat from the environment and transmits the heat to an internal unit located in the room to be heated. The internal air, forced through fans, receives the heat from the refrigerant and becomes heated. The cycle is repeated.
The choice of an air-conditioner should be well considered.
Important parameters are: the area of the room, exposure to sunlight, number, and direction of windows and doors, number of persons staying in the room and heat produced by electro technical devices. We recommend seeking of advice from an air-conditioning specialist. Professional method of installation of air-conditioners is very important as well.
Types of air-conditioners
Air-conditioning systems can be divided into the following categories in consideration of the fitting method:
· Window (compact) air-conditioners – for cross-installation on windows or walls. These air-conditioners perform functions of cooling or cooling and heating. They are equipped with exhaust grates, adjusted horizontally and vertically, which make it possible to direct effectively the stream of air and to supply fresh air from the outside. Range of cooling / heating efficiency: 2.1 kW to 7.9 kW.
· Wall (split) air-conditioners – consisting of two parts: an internal unit installed on the wall of the room, and an external unit installed on the facade, roof, balcony, etc. These air-conditioners perform functions of cooling, heating, ventilating, filtering, and drying. They are remotely controlled and provide users with a possibility to choose the mode for functioning of the device, temperature adjustment, and control of the working time. Range of cooling / heating efficiency: 2.0 kW to 8.8 kW.
· Ceiling/floor (split) air-conditioners - consisting of two parts: an internal unit installed on the wall under the ceiling or on the floor, and an external unit installed outside of the building (on the facade, roof, balcony, etc.). These air-conditioners perform functions of cooling, heating, ventilating, filtering, and drying. Remotely controlled. Range of cooling / heating efficiency: 4.1 kW to 15.8 kW.
· Ceiling/coffer (split) air-conditioners - consisting of two parts: an internal unit installed in the suspended ceiling and an external unit installed outside of the building (on the facade, roof, balcony, etc.). Locating of the internal unit in the ceiling allows for better planning of usable area and makes it possible to have the air distributed in an optimum way. These air-conditioners perform functions of cooling, heating, ventilating, filtering, and drying. Remotely controlled. Range of cooling / heating efficiency: 3.7 kW to 13.7 kW.
· Duct air-conditioners - perform functions of cooling, heating, filtering, drying, and ventilating. An external unit is installed outside of the building, and an internal unit is installed in the suspended ceiling. If one internal unit is used, it is possible to provide air-conditioning for several rooms or many areas. Air is distributed through a system of ducts located in the suspended ceiling. Duct air-conditioners can function with fresh, internal, or mixed air. The system is economical and discrete. The duct system for air distribution provides users with an optimum distribution of air in the rooms. Range of cooling / heating efficiency: 2.4 kW to 18.2 kW.
· Freestanding, high-performance air-conditioners – used in technical rooms, e.g. in server rooms, where it is necessary to maintain stable air temperature, so that the usually very expensive electronic equipment is not damaged during work. The device has a large cooling efficiency: 9 to 12 kW.
Pros and contras
Medical specialists warn that we cannot exaggerate with cooling.
The optimum temperature amounts to 20-24°. It has been proved that this temperature provides the best conditioning for functioning of human body. If however, we would enter a strongly chilled room, coming directly from heat, and excessively cool our sweating and heated body, we can rely on a cold.
The air we breathe should have an appropriate humidity rate and be free from dust, a strong allergen.
It is an undoubted advantage of air-conditioning systems that they destroy germs.
Modern air-conditioners are equipped with special filters, which remove impurities from the air and prevent harmful germs from spreading out. It is a favourable condition, especially for allergic persons: ill people are not exposed to pollens, fungi, saprophytes and other microorganisms, which – inhaled with the dust – often cause various allergies.
Yet, older models of air-conditioners are not equipped with filters. Fungi and bacteria develop in the ducts of the installation. Then, they are dispersed in the room every time when the device is switched on. In order to avoid it, the openings in the ventilating system should be thoroughly washed with warm water with soap once a month.
The disadvantage of air-conditioning system is that they desiccate the air.
In an office with good air-conditioning, air humidity falls almost to zero. Its level is additionally lowered by various electronic devices, such as computers, fax machines, or copying machines.
This is the way our skin, which very quickly loses water, is dried, and contracted after 8 hours of work. Sebaceous glands receive than a signal for intensive work, so the epidermis has an ugly glance at the same time. Red stains, eczema, and purulent spots can appear on the face.
Air cleaners
Speaking about ventilation and air-conditioning, it is also worth to mention air cleaners. These devices effectively eliminate bacteria and viruses up to 99.99%, can clean air through decay of scent molecules, and effectively remove the scent of cigarette smoke.
A huge advantage – not without an influence on our health – is the fact that air cleaners fill the environment with negative ions, such as occur in woods and near Mountain Rivers.
Do you know that:
the Japanese technician Kouzi Ichigaya has designed a special shirt for times of heat, equipped with fans and fed via a USB wire.
There are fans located on both sides of the rear part of the shirt, cooling the parts, which adhere most to the chair – in the designer’s opinion; this should enhance the work comfort. The speed of rotation of both fans can be adjusted with the attached USB wire with a special regulator.
The air-conditioned shirt can be also fed by four AA batteries or a car adapter. At present, short-sleeve shirts in versions for ladies and gentlemen are available.
