The boiler efficiency calculator consists of two concentric circles made from cardboard, and coated in a thin plastic film and attached together by a central metal ring. The top circle features in the centre "BOILER EFFICIENCY CALCULATOR" and the manufacturer information. Below this is a set of instructions on its use, while above there is a section for making calculations based on "Flue Gas Temperature, Oil, Natural Gas, Excess Air and Waste Percentages ranging from 65 to 45 percent. This section has a central strip cut out for viewing the values found on the lower slide. The inner circle, which is fixed in place, displays a selection of numerals and fractions which can be lined up with the appropriate sections on the top circle to give an accurate efficiency reading. The digits on this slide feature in a circular pattern around the entire card.
The back of the slide chart displays a series of instructions, diagrams and formulae relating to the calculation of heat loss in steam generating units and the causes of this including radiation, dry gasses, moisture and hydrogen.
In centre of slide, "BOILER EFFICIENCY CALCULATOR" and "Babcock & Wilcox, Canada"