An isothermal air curtain for isolation of smoking areas in restaurants.

An isothermal air curtain for isolation of smoking areas in restaurants was designed, built and evaluated in a test facility using oil-smoke visualisation and tracer measurements. The test facility was a ventilation test room set up as a small restaurant, with tables, chairs, person simulators (cylindrical heat sources) and balanced mechanical ventilation. Fresh air was supplied in the non-smoking section of the room, exhaust air drawn from the smoking area, and the air curtain was attached to the ceiling between the two sections. The air curtain was a plenum chamber with adjustable slot width and mounting angle fed by a supply fan drawing air from the smoking section of the room. For reasonable room ventilation rates for a restaurant ( 11 l/s per person supply and exhaust air), the optimised air curtain yielded tracer concentrations in the non-smoking section as low as 5 - 10 % of the values measured at the same time in the smoking section. The limiting factor in the performance of the curtain was found to be the ability to properly supply enough air to the clean-air side of the curtain to prevent recirculation of polluted air from the smoking area into the non-smoking section. This study demonstrates that an isothermal air curtain solution to control contaminant spread need not necessarily require excessive ventilation rates and prohibitive operating costs.