(5)Safety Ventilation. - (a) Every oven or drier shall be provided with a positive and effective safety ventilation system using one or more motor-driven centrifugal fans so as to dilute any mixture of air and any flammable substance that may be formed within the oven or drier and maintain the concentration of the flammable substance in the air a safe level of dilution.(b)The safe level of dilution referred to in clause (a) shall be so as to achieve a concentration of the concerned flammable substance in air of not more than 25 per cent of its lower explosive limit :Provided that a level of concentration in air upto 50 per cent of the lower explosive limit of the concerning flammable substance may be permitted to exit subject to installation and maintenance of an automatic device which-(i)shows continuously the concentration of the flammable substance in air present in the oven or drier at any instance;(ii)sounds an alarm when the concentration of the flammable substance in air in any part of the oven or drier reaches a level of 50 per cent of its lower explosive; and(iii)shuts down the heating system of the oven or drier automatically when the concentration in air if the flammable substance in any part of the oven or drier reaches a level of 60 per cent of its lower explosive limit, is provided to a oven or drier and maintained in efficient working condition.(c)No oven or drier shall be operated without its safety ventilation system working in an efficient manner.(d)No oven or drier shall be operated with a level of dilution less than what is referred to in clause (b).(e)Exhaust dusts of safety ventilation system should be so designed and placed that their dust discharge the mixture of air and flammable substance away from the work-rooms and not near windows or doors or other openings from where the mixture could re-enter the work-rooms.(f)The fresh air admitted into the oven or drier by means of the safety ventilation system shall be circulated adequately by means of circulating fan or fans through all parts of the oven or drier so as to ensure that there are no locations where the flammable substance can accumulate in the air become pocketed to any dangerous degree.(g)Throttling dampers in any safety ventilation system should be so designed by cutting away a portion of the damper or otherwise, that the system will handle atleast the minimum ventilation rate required for safety when they are set in their maximum throttling position.
