Office ventilation: sanitary standards of the supply and exhaust system, room standards

The working capacity of an office worker directly depends on the microclimate in the room. According to medical research, the air temperature in the office should not exceed 26 degrees, while in practice in buildings with panoramic windows and an abundance of equipment, it can go off scale for 30 degrees. In the heat, the reaction of employees is dulled, fatigue increases. The cold also affects the ability to work badly, causing drowsiness and lethargy. Lack of oxygen and high humidity create unbearable conditions for employees, lowering labor productivity, and hence the profitability of the enterprise.

To maintain the optimal temperature and humidity conditions, an office ventilation system is installed.

Office ventilation requirements

The ventilation of the office building must meet the following requirements:

• providing an inflow of fresh clean air;
• removal or filtration of exhaust air;
• minimum noise level;
• availability in management;
• low power consumption;
• small size, the ability to harmoniously fit into the interior.

The load on office climate systems is much higher than that of household air systems. It is required to qualitatively remove excess heat and carbon dioxide emitted by equipment and employees, to supply clean and filtered air at a given temperature.

Previously used natural ventilation systems in offices today are not able to provide conditions regulated by sanitary standards. Natural ventilation cannot be controlled, its efficiency is highly dependent on the parameters of the air outside. In winter, this method threatens with cooling the room, and in summer with drafts.

Widely used in the construction of office buildings, modern hermetically closing windows and doors, continuous panoramic glazing prevent the passage of air from the outside, causing its stagnation and deterioration of people's well-being.

All requirements for ventilation of office premises are specified in SanPiN (Sanitary rules and norms) 2.2.4.

According to the document, the humidity in the premises should be:

• at a temperature of 25 degrees - 70%;
• at a temperature of 26 degrees - 65%;
• at a temperature of 27 degrees - 60%.

Recommended air temperature 22 - 24 degrees with humidity 40 – 60%.

The following ventilation standards have been developed in offices, taking into account the purpose of the premises, in cubic meters per hour per person:

• manager's office - from 50;
• conference room - from 30;
• reception - an average of 40;
• meeting room - 40;
• staff offices - 60;
• corridors and lobbies - at least 11;
• toilets - from 75;
• smoking rooms - from 100.

SanPiN ventilation of office premises also regulates the air speed of 0.1 m / s, regardless of the season.

As a rule, ventilation of small office premises is realized with the help of several supply units. If in the hot season the supply ventilation of the office is not able to lower the air temperature below 28 degrees, additional air conditioning is required.

Separate air handling units are needed in conference rooms. Additional exhaust devices - in toilets, smoking rooms, corridors and lobbies, copy rooms. Mechanical exhaust from office rooms is necessary if the area of ​​each is more than 35 sq. meters.

If the total area is not more than 100 sq. meters and it has 1-2 toilets, natural ventilation is allowed in the office through the vents. Supply and exhaust ventilation is installed in offices of medium and large sizes.

Office ventilation system project

A number of functions are assigned to the ventilation system of an office building. Therefore, when designing, many factors are taken into account, regulated by the rules of SNiP ventilation of office premises No. 2.09.04.87 and 2.04.05.91. The system is assembled from units of different cost, functionality and design. The task of the designers is to select them correctly.

The following points are agreed with the customer:

• location of the ventilation unit;
• location of ventilation ducts;
• power of the electrical system, the ability to supply water;
• the need and ways of a drainage system;
• access to equipment after installation;
• the ability to change the design.

Design of ventilation systems for offices includes:

• calculations of heat flows for each individual room, depending on the architectural features, purpose, taking into account the technical specifications for the project;
• calculation of air exchange;
• axonometric communication diagram;
• aerodynamic calculation, which allows to determine the cross-sectional area of ​​air ducts and pressure losses along the network;
• selection of all the necessary equipment for completing the ventilation system in the office;
• calculation of the power of the heater in the supply unit;
• preparation of a package of design documents.

The technical equipment is selected simultaneously with the preparation of the project and takes into account all the customer's requirements. A properly configured ventilation system in any office increases employee productivity by 20% or more.

Components for office ventilation systems

Air ducts

Air delivery to the room and its removal is carried out through the air duct system. The duct network contains directly pipes, adapters, splitters, bends and adapters, as well as diffusers and distribution grilles. The diameter of the air ducts, the resistance of the entire network, the noise from the ventilation operation and the power of the installation are closely interrelated. Therefore, for optimal ventilation in the design process, it is necessary to balance all indicators. This is a difficult job that only professionals can do correctly.

The air pressure is calculated taking into account the total length of the air channels, the branching of the network and the cross-sectional area of ​​the pipe. The fan power increases with a large number of transitions and branches. Air velocity in office ventilation systems should be about 4 m / s.

Air ducts are assembled from flexible corrugated pipes or rigid metal or plastic. Flexible pipes are easier to install. But they resist the movement of air more strongly and buzz. Therefore, flexible pipes are used in small offices. Sometimes the main canals are made of rigid pipes, and the branches to the cabinets are made of flexible ones. But large systems are assembled from rigid pipes.

Air intake grilles

Installed in the place where air from the street enters the ventilation duct. The grilles protect against insects, rodents and precipitation from entering the pipe. Made of plastic or metal.

Air valves

Prevents wind blowing out when the ventilation system is off. Often, an electric drive controlled by automation is supplied to the valve. In order to save money, manual drives are used. Then a spring-loaded check valve or "butterfly" is adjacent to the valve in order to shut off the ventilation duct exits for the whole winter.

Air filter

Cleans the supply air from dust.As a rule, coarse filters are used, which retain up to 90% of particles with a size of 10 microns. In some cases, it is supplemented with a fine or extra fine filter.

The filtering surface (metal mesh or artificial fibers) must be cleaned periodically. The filter contamination is determined by pressure sensors.

Heater

It is used for heating outdoor air in winter, it can be electric or water.

Electric heaters have some advantages over water heaters:

• simple automatic control;
• easier to assemble;
• does not freeze;
• easy to maintain.

The main disadvantage - high price of electricity.

Water heaters operate on water with a temperature of 70 - 95 degrees. Disadvantages:

• complex automatic control system;
• bulky and complex mixing circuit;
• the mixing circuit requires special care and supervision;
• may freeze.

But with proper operation, it provides significant cost savings compared to an electric heater.

Fans

One of the most important components of the entire ventilation system. The main parameters when choosing: performance, pressure, noise level. There are radial and axial types of fans. For powerful and branched networks, radial fans are preferable. Axial ones are more productive, but they give out weak pressure.

Muffler

Installed after the fan to suppress noise. The main source of noise in an office ventilation system is the fan blades. The filling of the silencer is usually mineral wool or fiberglass.

Distribution grilles or diffusers

Installed at the air duct exits to the premises. They are visible, therefore they must fit into the interior and ensure the spread of air currents in all directions.

Automatic control system

Monitors the operation of ventilation equipment. Usually installed in an electrical panel. Starts fans, protects against freezing, notifies about the need to clean filters, turns on and off fans and heaters.

Climatic equipment for offices

• 

  Supply ventilation unit for office... Pushes fresh air from the street directly into the office. Air outflow occurs by displacing it into corridors and lobbies. With an area of ​​more than 40 sq. meters the air is evacuated directly from it. Supply units for ventilation of offices are used for areas up to 100 sq. meters;

• Supply and exhaust office ventilation systems... It is the most widely used type of equipment for air evacuation, purification and delivery. The set may include cooling or heating devices, humidifiers. The complete set is very diverse, but the supply and exhaust ventilation of the office should be calculated and installed by professionals. Automatic control over functionality reduces power consumption and increases efficiency;
• Ducted ventilation system in the office... Ducted air conditioners with outdoor air admixture are installed in small and medium-sized offices. It is combined with supply and exhaust equipment, which brings the outside air temperature to the required one. After which it is served in the rooms;
• Central air conditioning and ventilation in a large office... In large office buildings, the climate is controlled by chiller-fan coil systems and multi-zone VRF systems. The latter consist of many indoor units that provide different temperatures and humidity in the premises. Central air conditioners represent supply and exhaust ventilation in offices with cooling and heating units. This type of climate systems is suitable for large offices that are not divided into separate offices.

Supply and exhaust ventilation of the office

Duct ventilation of the inflow-exhaust system is used for rooms up to 600 sq.meters, since the capacity of the supply and exhaust ventilation of the office is up to 8 thousand cubic meters per hour.

According to the norms of SanPiN ventilation of office premises, 60 cubic meters of air per hour must be supplied per person.

SNiP ventilation of office premises requires air exchange:

• inflow 3.5 times per hour;
• outflow 2.8 times per hour.

The equipment is usually hidden behind the suspended ceiling of the utility room. Air is distributed through offices by a system of ventilation ducts, the exits of which are hidden behind diffusers or grilles.

The inflow of air from the street with the supply ventilation of the office is carried out at a height of two meters above the soil surface. The air is passed through the cleaning system, if necessary, its temperature is reduced or increased (electric or water heater).

The exhaust air is outflowed into a ventilation shaft or through a pipe, the end of which is located 150 cm above the roof.

To reduce energy consumption, the supply air is heated by a recuperator. It is a heat exchanger in which the heat from the exhaust air is transferred to the fresh air. Recuperators for office ventilation are used rotary and plate. The first ones have an efficiency of more than 75%, they work in bitter frosts. But during operation, about 5% of the exhaust air enters the room back.

Plate recuperators are inexpensive, their efficiency is not more than 65%. But they freeze up, you have to provide heating.

All the necessary equipment for air handling in the supply and exhaust system is located in one relatively small case. Duct ventilation of office premises is a combination of several modules.

To ensure the required air temperature in the office space, supply and exhaust ventilation is supplemented with air conditioners. Depending on the characteristics of the building, it can be several split systems or multisplits.

Office ventilation

Ventilation of a small office building can be provided by a ducted air conditioner. In addition to cooling and heating the air, duct systems supply the halls with a certain amount of fresh air from the street. To implement this function, the duct air conditioner is equipped with additional equipment that mixes air. That is, the equipment both airs and ventilates the office in accordance with the norms.

This scheme works like this:

Outside air is fed into a mixing chamber in front of the air conditioner, where it mixes with the exhaust air. The mixture is fed into the air conditioner, cleaned, brought to the required temperature and sent through the ventilation ducts to the offices. The air from here moves to the mixing chamber and further along a circular cycle.

The case of the air conditioner is hidden above a false ceiling or in a utility room.

The advantage of the duct ventilation system for office premises is its invisibility. But it excludes the possibility of varying the air temperature in different rooms.

Air handling units in combination with VRF systems for the office

On large areas, the installation of duct equipment is difficult, therefore, maintenance of large buildings is carried out by supply and exhaust ventilation units for offices in combination with chiller fan coil units and VRF systems.

The capacity of such equipment can reach 60 thousand cubic meters per hour. Ventilation and climatic equipment is installed on the roof of the building or in separate rooms.

The installation consists of many modules, which are assembled depending on the needs of the enterprise and taking into account the norms of ventilation of offices. The kit may include:

• fan chamber;
• recuperator;
• noise absorber;
• mixing chamber;
• block with filters.

Air movement is carried out along a branched air duct system. The air temperature in the building is maintained by fan coil units or VRF systems.

VRF- is a multi-zone climate system capable of maintaining the microclimate of an entire building.It is possible to differentiate the temperature in different rooms. In each room, an internal module is installed that keeps the temperature within the specified limits. There are no temperature changes typical for household air conditioners. Indoor modules can be of any type (floor, cassette, ceiling).

The chiller heats or cools the refrigerant ethylene glycol. Which is fed to the heat exchanger - fan coil unit with forced air movement. Fan coil units are located directly in the office rooms. In order for the coolant to move at a given speed, the system is complemented by a pumping station. Many offices and halls can be connected to one ventilation and air conditioning scheme. And not all at once, but as the need arises.

Central air conditioners for ventilation of offices

Central air conditioners are classified as industrial climatic technology. They are installed in accordance with SNiP and provide ventilation and air conditioning of office premises. In the air conditioner module, the air is brought to the required parameters of temperature and humidity. Air recirculation is carried out (mixing of waste and fresh air), including partial air recirculation. After processing, the air is supplied to the premises through the air duct system.

The advantage of central systems is the absence of internal modules. At the same time, the air conditioner itself is a rather bulky structure that requires a separate room. Air ducts are also needed quite voluminous. At the same time, the temperature throughout the building will be maintained at the same level.