Roof fans are designed for decentralized obscheobmenpoy extracts from the upper zone of the premises, directly under the roof. Typically, roof fans are working with direct intake air from a room without air ducts.
Most applicable roof fans for exhaust from the shops with no significant heat, such as welding workshops, garages and so n Use appropriate roof fans and for rooms with heat, while gassing. Roof fans are quite applicable in the shops of the chemical industry, in foundries and smelting plants.
In addition to the general exchange hood, roof ventilators can be used by aphid removal of air from some local shelters, such as curtains or capacious umbrellas.
In all cases, the installation of roof fans to provide them with convenient service. Typically, these fans are operated from the roof, which should provide the corresponding outputs on the roof, conversions, and fencing.
Ending with a brief overview of the fans should pay attention to the lack of fans with low productivity of the order of 50-100 K / h. The need is evident to them.
Ventilation boxes for packaging of radioactive substances requires air flow of about 10 - 20 LR / h on a box while creating vacuum in the duct at the box about 40-50 kg/m2.
For ventilation boxes with small air exchange and high resistance in the absence of unproductive fans following scheme is proposed.
Box attached to an ordinary fan with a capacity of about 400-500 ig3 / /. Part of the air is sucked out of boxing (10-20 n / h), the rest of the air comes out of the room through a special check valve that creates a constant vacuum in the duct 40-50 kg/m2.
Information letter in 1965, the State Design Institute Santehproekt excludes continue the installation of fans and air ducts of any control devices (dampers, throttle valves, etc.).
In the same letter is recommended for start-up commissioning to ensure the design volume of air in case of need during the installation of flanged joints throttle washers. However, the author still believes the installation of control devices for the fans is justified.
Typically, a centrifugal fan gate is installed on the discharge side, right at the exhaust port. It is constructive, but in some cases unacceptable for sanitary reasons.
Even the best design of valves and dampers have leaks, sometimes quite substantial. Through these leaks in the room where the fan is ejected air. If the removed ventilation air is not highly toxic substances, emissions of air in the room can be admitted. In the presence of toxic substances in the air may be poisoned.
In all cases, removing toxic substances (cyan, arsenic, selenium, tellurium, lead, mercury, n, etc.) is recommended to install dampers or throttle valves on the suction side, regardless of the location of the fan, and take care of the complete sealing of pressurized air.
Because of the danger of penetration of toxic substances is forbidden strip of pressure air through the working areas. In an extreme case, such a seal is permissible with the adoption of special precautions and side air ducts and the maximum germspiatspi. Protecting them or corrosion.