FI95169B - Process for reducing the radon content of air in a room - Google Patents

Description

95169

METHOD TO MINIMIZE ROOM CONCENTRATION

The invention relates to a method for minimizing the radon content of room air by means of mechanical ventilation.

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Radon gas released from the soil is harmful to humans in high concentrations. The amount of radon gas varies greatly from state to state and region to region. The national average radon concentration in room air is about 100 Bq / m3 in Finland, Sweden 10 and Norway, and about 50 Bq / m3 in the United States, Canada and Germany. The guide values for the permissible radon concentration in different countries also vary to some extent, and in the EC area, for example, the maximum concentrations are 200 Bq / m3 for new dwellings and 400 Bq / m3 for old dwellings.

15 The main mechanism for the transfer of radon is the convection flow of radon-containing pore air into the room air through anti-ground parts of the building. The convection flow of radon is dependent on the pressure difference and increases as the vacuum of the indoor air increases with respect to the soil (- outdoor air) if there are leaks into the room space at the bottom. The vacuum is caused by temperature differences, wind and the ventilation system.

: · V 25 The aim is to reduce and minimize the amount of radon gas>: by different methods. Concentration of structures in repair »: construction is mainly considered as a complementary part of other measures. When ventilating the building floor, the problem is: possible cold disadvantages of the subfloor, increasing moisture damage. Number of methods and cost of the method. Removing a radon source or compacting the soil are expensive solutions and * 'rarely come into question.

·· »# 0; In a standard mechanical supply and exhaust air system: 35 a building or room is intended to be underweight.

This is achieved by choosing the total supply air flow * in single-storey houses 20% (15%) and in double-storey

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»2 95169 houses 25% less total exhaust air flow. In this way, the aim is to ensure that the building remains under pressure in different weather conditions. A slight vacuum of the interior is sought so that the structures do not condense 5 moisture that damages them. According to the design guidelines, 2 Pa for a single-storey building and 4 Pa for a two-storey building are selected as the pressure difference across the outer shell by ventilation. The pressure differences are achieved in a dense single-storey house (leakage rate QM is 1) with a 15% airflow difference, and in a two-storey house with a 25% airflow difference. The selected pressure difference corresponds to a windless and temperature-free situation. In practice, the formed vacuum proportional to the density of the building is not measured in connection with the adjustment work. Typically, there is a large variation in the pressure difference between the indoor air and the outdoor air in the building 15, and the pressure difference is generally too large to minimize radon in the room air.

In order to minimize the radon concentration, it is difficult in practice with current systems to adjust the supply and exhaust air to almost the same level so that the controls are correct and the control values are maintained. The pressure ratios of dwellings also vary over time as a result of changes in weather conditions, regardless of the adjustments. Mechanical ventilation increases the underpressure of the lower part and reduces the overpressure of the upper part.

The object of the invention is to provide a method for minimizing the radon concentration in room air, by means of which method the average level of radon concentration is kept as low as possible.

The object of the invention is achieved by a method which is characterized by what is stated in the claims.

According to the invention, the amount of supply air entering the room and the exhaust air leaving the room is continuously adjusted on the basis of the pressure difference between the indoor and outdoor air so that the vacuum inside the room is as small as possible, preferably 0-5 Pa. In this case, the release of radon from the soil can be considerably reduced, because ventilation provides a permanent minimum pressure difference across the structure 5, so that the passage of radon-containing air through the leak points of anti-ground structures into the interior is minimized. The air volumes are adjusted stepwise or steplessly. As the vacuum of the room increases, the amount of supply air is increased. The proportion of exhaust air is reduced if the supply air supply is not sufficient.

10 As the vacuum decreases, the opposite is true.

In order to minimize the inflow of radon gas caused by leakage air from the ground, the differential pressure regulator (microprocessor) of the room with mechanical supply and exhaust ventilation is maintained with fans, control dampers or other air volume control device. the vacuum inside the building or room with respect to the outside air as the external or internal factors of the building change and the ventilation capacity changes as required. The weight ratio of the building is adjusted by changing the inlet and outlet proportion of the room ventilation so that the desired pressure ratio is maintained in normal situations and also in special situations. When using a cooker hood, the vacuum caused by it 25 is preferably reduced by means of a differential pressure regulator by increasing the amount of supply air. Similarly, when using a fireplace, the amount of supply air is increased by means of a differential pressure regulator, whereby the operation of the fireplace is improved. When using the method, the pressure difference of the space is maintained at its set value regardless of factors that change the air volumes, such as weather conditions, fouling of the filters and / or fogging of the heat recovery cell.

It is difficult in practice to adjust the supply and exhaust air almost equally so that the adjustments are correct and maintained. For this purpose, a digital differential pressure controller is preferably used. The required algorithms, calculation procedures, signal filters and logics are programmed for the controller. Occasional disturbance pressures are handled programmatically by the controller and thus prevent the occurrence of a permanent control deviation. Occasional disturbance pressures are e.g.

5 window vents, quick door openings and closes, and gusts of wind. The pressure variation due to disturbance pressures has to be accepted in the control, because the control system is slow. The control should also interpret situations where control is impossible, such as during gusts of wind (disturbance -10 large and frequency and variation of pressure variation). In such a situation, the controller returns the ventilation to the selected power and the basic ductwork adjustment (to equilibrium or slightly underpressure).

The invention will now be described in more detail with reference to the accompanying drawing, in which Figure 1 shows a schematic diagram of an apparatus for applying the method according to the invention, and Figure 2 shows an apparatus for applying the method according to the invention in more detail and schematically.

The schematic diagram according to Fig. 1 shows a room 1, a differential pressure regulator 2, a differential pressure gauge 4 and a supply air volume control device 5 and an exhaust air volume control device 6. The differential pressure gauge 4 continuously measures the pressure difference between the room and the outside air. By means of the differential pressure regulator 2, the devices 5, 6 are continuously regulated so that the vacuum prevailing inside the room is as small as possible, preferably 0-5 Pa.

Figure 2 shows an application of the IV equipment used in repair sites. The hardware in this application includes at least the following parts; differential pressure controller 2, differential pressure transmitter 4, supply air fan 5, extract air fan 6, cooker hood 3, heat recovery device 7, ventilation control switch 8 and electrical and control center 9. When using the apparatus 5 95169, the differential pressure transmitter 4 continuously measures the -eroa. The differential pressure controller 2 changes the air volume (control message - damper position - air volume) of the inlet fan 5 and the exhaust fan 6 steplessly based on the measurement of the differential pressure transmitter 4 so that the pressure difference remains in the building at the differential pressure controller 2 setpoint, preferably 0-5 Pa vacuum. As the vacuum increases, the supply air damper 10 of the supply air fan opens. The exhaust air damper outlet damper 11 starts to close if the supply air damper does not open enough. As the vacuum decreases, the opposite is true. From the pressure regulator, the degree of opening and closing of the damper pressure control can be limited. The required ventilation capacity is selected from the pressure regulator. The normal ventilation operating switch 8 is maintained at a sufficiently high ventilation power. The differential pressure controller has an operating switch with which the differential pressure controller can be switched off, whereby the supply and exhaust air system is set to the selected ventilation output. When using the cooker hood 3, the differential pressure control adjusts the differential pressure in the room immediately and the dampers 20 operate beyond the limits.

Another option is to use dampers that do not completely shut off the flow but limit it: · flow between a certain number of extreme positions. The differential pressure controller 2 is a microprocessor-based programmable controller.

. *. If necessary, the controller can be used to change the measuring time, the setting time, the values of the interfering pressure to be filtered, the ventilation capacity (damper position) and the restriction on opening and closing. The controller has a display for the pressure difference.

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The invention is not limited to the preferred embodiment shown, but may vary within the scope of the inventive idea formed by the claims.

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Claims (5)

95169 A method for minimizing the radon content of room air by means of mechanical ventilation, characterized in that the amount of exhaust air entering the room air (1) and the exhaust air removed from the room is continuously adjusted by the differential pressure gauge (4) continuously measured by the indoor and outdoor air pressure the vacuum inside is as low as possible, preferably 0-5 Pa. Method according to Claim 1, characterized in that the amount of supply and exhaust air is adjusted by means of a digital differential pressure controller (2) in order to maintain the differential pressure. Method according to Claim 1 or 2, characterized in that the vacuum caused by the cooker hood (3) is reduced by means of the differential pressure controller (2) by continuously increasing the amount of supply air 20 on the basis of the measured pressure difference. » Method according to one of Claims 1 to 3, characterized in that when the fireplace is used, the amount of supply air is increased on the basis of the pressure difference continuously measured by means of the differential pressure controller, whereby the operation of the fireplace is improved. Method according to one of Claims 2 to 4, characterized in that the digital differential pressure controller returns the ventilation to the basic control when, on the basis of the circumstances, control based on the differential pressure is impossible. * 95169