Document JvaX3npr6o7aymYvEX4K7Qv6

SAFETY ENGINEERING TABLES TABLE 45-L VENTILATION RATES FOR OPEN-SURFACE TANKS Process MmitwMB Ventilation Rato efm Per Sq Ft Hood Opening Hood Hoed' One Two Three Foot Open Open Open Op*n Side Sides Sides Minimum Ventilation Rate elm Per So Ft Tank Area Lateral Exhaust (Note 1) ------ Tank Width Tank Length W/L 0-0 24 AB W/L 0 2S-0 49 AB W/L 0 50-1.0 AB Plating Chromium (Chromic Acid Mist) 75 Arsenic (Arsine) . 85 100 90 125 100 175 150 125 175 150 200 175 225 90 130 110 150 130 170 Hydrogen Cyanide . 75 100 125 175 125 175 150 200 175 225 Cadmium , 75 100 125 175 125 175 150 200 175 225 Anodizing..................... 75 100 125 175 125 175 150 200 175 225 Metal Cleaning (Pickhng) Cold Acid....................... Hot Acid............................. 65 75 90 100 100 125 150 175 90 125 130 175 no ISO 150 200 130 175 170 225 Nitric and Sulfuric Acid ... 75 100 125 175 125 175 150 200 175 225 Nitnc and Hydrofluoric Acid 75 100 125 175 125 175 150 200 175 225 Metal Cleaning (Degreasing) See Note 2 Metal Cleaning (Caustic or Electrolytic) Not Boiling......................... 65 90 100 150 00 130 110 150 130 170 Boiling ..................... 75 100 125 175 125 175 150 200 175 225 Bright Dip (Nitric Add) 75 100 125 175 125 175 150 200 175 225 Stripping Concentrated Nitric Acid 75 100 125 175 125 175 150 200 175 225 Cone. Nitnc and Sulfuric Acid................................. 75 100 125 175 125 175 150 200 175 225 Salt Baths (Molten Salt) ... 50 75 75 125 60 90 75 100 90 no Salt Solution (Parkenze, Bondenze, etc.) Not Boiling..................... 90 90 100 150 90 130 no 150 130 170 Boiling................................. 75 100 125 175 125 175 150 200 175 225 Hot Water (if vent, desired) Not Boiling . ... Boiling 50 75 75 125 60 90 75 100 90 no 75 100 125 175 125 175 150 200 175 225 ASHRAB Guide and Data Book. 1962, Chapter 21 Used bp permission Note 1 Column A refers to tank with hood along one side or two parallel sides when one hood is against a wall or a baffle running length of tank and as high as tank is wide, also to tanks with exhaust manifold along center line with W/Z becoming tank width in W/L Ratio* Column B refers to free standing tank with hood along one side or two parallel sides Note 2 Complete control of the vapors and mist from degreasing operations requires the same ventilation rates as recommended for pickling However, the solvents employed in degreasing operations are relatively volatile, and the solvent loss caused by evaporation increases rapidly as the exhaust rate at the tank increases For this reason, perfect control is usually sacrificed in favor of lower solvent evaporation rates Where solvent loss does not present an important cost or operating problem, the exhaust rates given for pickling should be adhered to, but where solvent loss must be kept at a minimum, an exhaust rate of 50 cfm per sq ft of tank area is commonly employed. Where this rate is used, control will be adequate only if the tank is located in an area free of drafts and if the deceasing operations are earned out in accordance with a rigid schedule 45-30