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5.3.1 In workshops where the volume per worker at the workplace is less than 20 m3, at least 30 m3 of fresh air per person per hour must be ensured; if the volume is between 20 and 40 m3, at least 20 m3 of fresh air per person per hour must be provided; when the volume exceeds 40 m3, it is acceptable to use air that enters through doors and windows for ventilation. In workshops equipped with air conditioning, at least 30 m3 of fresh air per person per hour must be ensured. Question: How can one ensure that each person receives no less than 30 m3 of fresh air per hour? 5.1.14 In workplaces where large amounts of harmful substances may suddenly be released, or where chemicals that can cause acute poisoning or are flammable and explosive are used, automatic alarm systems and emergency ventilation facilities must be installed; the number of ventilation cycles per hour must be at least 12. The outlets of these emergency exhaust systems should be designed in such a way as to avoid affecting residents and passersby. Question: How is the exhaust ventilation rate of 12 times per hour calculated, and what power rating should the fan have?
For the first question, the number of people in the workshop × 30 m3/person-hour = X m3/hour. Fresh air is introduced using fans, right? As long as the total airflow generated by the fans is sufficient to reach this X value, that’s fine.
The air volume delivered by a fan is defined as the product of the wind speed V and the cross-sectional area F of the air duct. In the case of large fans, it is possible to measure the wind speed accurately using an anemometer, which makes it simple to calculate the air volume; the formula Q=VF can be used directly to determine this value. The number of fans required is determined by calculating the total air volume needed for the facility, based on the required number of air changes per hour in the selected rooms, and then using that figure to compute the appropriate number of fans. Calculation formula: N = V × n / Q, where: N – number of fans (units) ； V — Volume of the site (m3) ； n——air change rate (times/hour) ； Q — Air volume per fan of the selected model (m3/h). The selection of fan models should be based on the actual conditions of the factory building; it is advisable to choose fan models that match the dimensions of the original windows. A certain distance should be maintained between the fans and the wet curtains (they should preferably be installed on opposite sides of the roof ridge of the factory building) in order to achieve effective ventilation. The exhaust side should be kept as far away as possible from nearby buildings to avoid affecting the residents in those areas. If the air taken out from indoors contains substances that can pollute the environment, a **device** can be installed at the air outlet to absorb and collect such pollutants, thereby preventing environmental contamination
An air renewal system is a system that brings outside air into office buildings. 1. The fresh air system consists of a fan, air inlets, air outlets, as well as various pipes and connectors. The fan installed in the ceiling is connected to a series of exhaust vents through pipes. When the fan starts, the polluted air inside the room is expelled outside via these exhaust vents and the fan, creating a negative pressure inside the room. Fresh air from outside then enters the room through the intake vents located above the window frames (between the window frames and the walls). An automatic timing switch is used to control the periodic operation of the fan, which helps save energy, prevents 24/7 operation, and extends the lifespan of the fan, thereby allowing those inside to breathe high-quality fresh air. 2. Benefits of using a fresh air system: 1) Enjoy fresh air from nature without having to open windows ； 2) Avoid \"air conditioning syndrome\"” ； 3) Prevent indoor furniture and clothing from molding ； 4) Eliminates the harmful gases that are released slowly over time as a result of indoor decorations, contributing to human health ； 5) Adjust indoor humidity to save on heating costs ； ------------------------------------------------------- Answering the second question, the accident exhaust at 12 times per hour is controlled by an automatic circulation timer switch, right?
This is a relatively technical question; it can be used as a reference for calculations.