Testo 310 & 320 make combustion analysis easier to perform, easier to control, and easier to understand. Testo 310 residential combustion analyzer represents a new class of instruments for Testo & provides exceptional value and expanded capabilities in combustion testing. Testo 320 is designed for the job site & for the contractor that expects more. Use it for basic testing & tuning of all types of boilers, heater or furnaces. Use it to set up and commission more complex multi-stage, or modulating heating systems.