Acute mercury pneumonitis.

Although poisoning by mercury has been recognised since the time of Ramazzini (1713), inhalation of sufficient mercury vapour to cause toxic pneumonitis is still an uncommon industrial accident.We report one such accident, which affected four men repairing a condenser in a power station, and following which we were able to make serial physiological and toxi- cological measurements. Description of the accidentFour contractors were sealing expansion leak joints inside the steam space of the low-pressure condenser of a turbogenerator at a power station.The space in which they were working measured 24 x 8 x 6 feet (-72 x 2-4 x 1 8 m).The turbine was being cooled by a flow of compressed air, controlled by a valve across which was placed a Kent ST/4 universal industrial manometer containing about 200 ml of mnercury.At 3 00 pm on 12 October 1974 the control valve was adjusted to supply more cooling air, at a temperature of 90°C and a flow rate of 500 cu ft/min (~14-2 m3/min).This caused mercury to be blown out of the manometer, vaporised and carried into the intermediate pressure cylinder which had walls at 260'C.Some of this air then passed to the low- pressure condenser in which the men were working at a temperature of 20°C.Although the loss of mercury was noted by the operator (and later established to have been approximately 100 ml), no action was taken at this stage because the spilled mercury was separated from the condenser by a 20 foot (-6 m) vertical pipe and also because it was assumed that the air flow was vented to the outside.However, it was subsequently found that the entire "