The popularity of the Boiler Operators Handbook has prompted the issue of a revised edition. Other than a relatively small number of developments, essentially associated with solid fuel firing methods using the fluidised bed technique, no radical changes have occurred since the first edition of the Handbook was issued in 1969. In revising a work of this kind there is a great temptation to omit practices that are now less common in the UK. In view of the enormous pressure on Global energy resources, however, the chapters dealing in methods of hand-firing have been retained in the hope that they may be of value to those in the less developed nations where energy problems are infinitely greater than ours. High combustion intensity boilers, commonly known as Package Boilers, of the Shell Construction design, have now much greater steam output than their predecessors and the need for high levels of maintenance and operating skills remain as essential as when this group of boilers first appeared on the market. Also the standard of water treatment required is probably higher than the Operator has been accustomed to. The Health and Safety at Work Act re-emphasised the continued need for adherence to the principles that ensure a pressure vessel be maintained in a safe condition at all times. Accordingly the revised edition of the Boiler Operators Handbook has en­larged its sections on Safety and the Clean Air Act.