tailieunhanh - ENCYCLOPEDIA OF ENVIRONMENTAL SCIENCE AND ENGINEERING - INDOOR AIR POLLUTION

tôi Không khí trong nhà Ô NHIỄM Phòng thí nghiệm công trình và thử nghiệm hóa học liên quan đến thủ tục có thể gây ô nhiễm không khí bên trong không gian bị chiếm đóng. Bản chất của các chất gây ô nhiễm rất khác nhau: độ ẩm cao từ phòng tắm hơi nước, mùi hôi từ phân tích hydrogen sulfide, khả năng ăn mòn của Alkalies và axit, tính hòa tan của acetone, tính chất bùng nổ của axit perchloric, mối nguy hiểm sức khỏe của aerosol vi khuẩn, và các tài sản độc hại của cacbonyl niken. Lý tưởng. | I INDOOR AIR POLLUTION PART 1 Laboratory work and chemical testing involves procedures that could contaminate the air inside occupied spaces. The nature of the contaminants varies widely high humidity from steam baths odors from hydrogen sulfide analyses corrosion capabilities of alkalies and acids solubility of acetone explosive properties of perchloric acid health hazards of bacteriological aerosols and poisonous properties of nickel carbonyl. Ideally best procedure is not to emit but the next best is to remove or exhaust directly and as close to the point of origin for safety of laboratory personnel and protection of property. To achieve this end the accepted methods used for containment and removal of contaminants is by restricting the contaminant procedures to within an enclosure or hood. Simultaneously the air is drawn across the hood face to capture and remove the contaminants before escaping into the room. In the design of a fume exhaust system utilizing hoods the following factors must be analyzed and evaluated Capture velocities Fume hood design Seven basic hood designs Makeup air source Air distribution Exhaust system Exhaust duct materials Exhaust air treatment Special systems. CAPTURE VELOCITIES Air flow rates required for hood exhaust systems are based on a number of factors the most important of which is capture velocity. For most applications these will range from 50 to 200 fpm. The lower figure is used to control contaminants released at low speed into relatively quiet room air 15 to 25 fpm . The higher figure is used to control contaminants released at high rates. Under special conditions hood face velocities as low as 25 fpm have been used with industrial type hoods. Conclusions regarding optimum face velocity selection are rather mixed. In conceptual design of a lab facility this is given much thought and argument especially when air conditioning is to be included. For every 1000 cfm of air exhausted through hoods 3 to 4 tons of refrigeration .