No more surprises: the testo 405i thermal anemometer with smartphone operation from the Testo Smart Probes series is ideal for carrying out measuring tasks in ventilation ducts. It is easy to use the anemometer to determine air velocity, temperature and volume flows. The testo 405i is also suitable for measuring indoor air velocity. Practical when, for example, you want to locate non-airtight windows. Cooling capacities and heating outputs can also be calculated when used in conjunction with the testo 605i thermohygrometer.