4.5　Ventilation Equipment and Air Ducts

4.5.1　Ventilators shall be selected according to the characteristics of the medium which they handle，and the following requirements:

a）When the temperature is higher than 80℃，the high-temperature resistant fans shall be selected.

b）When the air contains corrosive substances，the corrosion-resistant ventilators shall be selected.

c）When the air contains explosion hazardous substances，the explosion-proof fans shall be selected.

d）When the air contains extremely toxic substances，the special fans with good tightness performance shall be selected.

e）When the dust concentration is greater than 100mg/m3 or the air contains granular dust and fibers，the dust removal fans shall be selected.

4.5.2　If two or more fans are installed in one ventilation system to operate in parallel or in tandem configuration，they shall be of same model and have same operational performance.

4.5.3　Cross sections of air ducts should be sized in accordance with GB 50243.

4.5.4　The ventilation equipment，air ducts and fittings shall be made of anti-corrosion materials or arranged with corresponding corrosion-resistant measures according to the locating environment，and the temperature and corrosivity of gas or dust that they convey.

4.5.5　Air ducts for dust collection systems should be of circular steel ducts with air-tight and smooth connections and joints.Air ducts should be routed in a vertical or inclined（in an intersection angle larger than 45℃with the horizontal plane）way.Air duct runs routed in small inclined angle or horizontally routed should not be too long，and provisions shall be made to avoid dust accumulation.Air-tight cleaning holes shall be provided at locations near to the irregular-shape duct fittings where dust is prone to buildup.

4.5.6　Air ducts used to remove the air containing extremely toxic substances shall not pass through other rooms and passages.

4.5.7　Air ducts to handle the air containing highly toxic substances shall not pass through other rooms，if it is necessary，it shall be at negative pressure.All such air ducts shall be joined by welding，and shall not be installed with dampers.

4.5.8　Air ducts used to remove the air containing relatively toxic substances should not pass through other rooms.

4.5.9　For production buildings containing highly or highly toxic substances，individual air supply fan rooms shall be constructed.

4.5.10　Local exhaust equipment to handle the air containing extremely toxic substances shall be arranged in individual rooms.

4.5.11　Local exhaust equipment to handle the air containing highly toxic substances shall be arranged separately from the general exhaust equipment，and should be located in individual rooms that are isolated from the served production buildings or located outdoors.

4.5.12　Arrangement for air ducts of hot air heating，ventilation and air conditioning systems and fire dampers in production buildings and auxiliary buildings shall conform to GB 50016.

4.5.13　Air ducts that are connected with equipment subject to vibration（e.g.，fan and etc.）shall be provided with flexible joints.

4.5.14　For ventilation systems to handle the air containing harmful gas or dust，their exhaust outlets should be installed with conical cowls or rainproof funnel caps.