Testo 400 air flow kit to measure air velocity, volume flow, and air temperature in ventilation ducts and outlets. The Testo 400 universal measuring instrument and its hot wire probe, vane anemometer probe and pitot tube are low maintenance, easy to use, and maximize convenience when testing, adjusting and balancing air conditioning and ventilation systems. Ideal for Testing, Adjusting and Balancing (TAB) / (Retro)-Commissioning – Professionals (BSC / RCx) or Cleanroom Performance Tester (CPT) the Testo 400 Air Flow kit meets highest standards when it comes down to accuracy and durability for air velocity measurements on HVAC systems.