Oil Burner Combustion Testing Kits Components 1. Fyrite® CO2 Indicator – The Fyrite Carbon Dioxide Indicator measures the percent CO2 in a flue gas sample. 2. True Spot® Smoke Tester and Oil Burner Smoke Scale – With the True Spot Smoke Tester and Smoke Scale, you can get an accurate indication of smoke content in flue gas. 3. Fire Efficiency Finder/Stack Loss Slide Rule – The Fire Efficiency Slide Rule is a quick and easy way of determining combustion efficiency and stack loss from the results