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Volume flow hood

Light, precise and convenient: the testo 420 volume flow hood significantly facilitates volume flow measurement at larger air intakes and vents. At only 2.9 kg, it is the lightest volume flow hood on the market. And with the integrated flow straightener, the measuring instrument for volume flow measurement sets new measurement precision standards at swirl outlets.

This allows users to fulfil hygienic Indoor Air Quality and volume flow guidelines and stipulations in ventilation and air conditioning systems quickly and precisely, e.g. in industry, office rooms or in cleanrooms.

What the testo 420 volume flow hood has to offer you

  • Ergonomic: Exceptionally lightweight, weighing less than 2.9 kg (standard flow hood 610 x 610 mm, other sizes also available)

  • High-precision: Flow straightener significantly reduces common measurement errors at swirl outlets

  • Efficient: Fast set-up, easy handling and convenient operation via the testo Smart App

  • Compatible: Measurement, documentation and sending of reports in conjunction with the testo 400

Advantages of the testo 420 volume flow hood

  • Light: unique weight of less than 2.9 kg. You will feel the difference, particularly for frequent measurements.

  • Precise: air turbulence at swirl outlets is better channelled. This allows reliable measurement of the air flow.

  • Flexible: optional exchangeable hoods for a variety of measuring tasks.

  • Efficient: monitor measuring values and send them by e-mail directly on site via App.

  • Convenient: the tilting display makes it easier to read out the measuring values. By removing the instrument, and with the corresponding accessories, you can comfortably carry out pressure and Pitot tube measurements too.

  • Smart: the App allows you to use mobile devices as a second display or remote control.

  • Compatible: Measure and manage measurement and customer data by integrating the testo 400.

testo Smart App

Volume flow measurement via App

With the practical testo Smart App on your smartphone/tablet, you can fully exploit the capabilities of the volume flow hood.

For instance, you can then operate the measuring instrument remotely and also manage your measurement and customer data, and as an added bonus, reports can be sent directly on site via e-mail.

Now new:

PRO measuring program for increasing the efficiency of your applications

Find out more

Monitoring of readings

via graphic progression display and remote control of the testo 420

Creation of reports/documentation

with photos or comments and sending them via e-mail


of total volume flow and air exchange rate


and also storage and management of measurement and customer data

Range of approx. 20 m

in free field conditions via Bluetooth Low Energy

With these advantages, you'll be able to measure volume flow accurately

In addition to its light weight and the flow straightener, the following features will make your everyday work easier:

  • Ergonomic handles

  • Tiltable and removable display

  • Funnel-shaped tension rod sockets for quick, easy set-up

  • Trolley included for safe transport

  • App integration for smartphones and tablets. Via Bluetooth, these become a second display and a remote control. Particularly practical for the safe use of a tripod for high ceilings.

  • Convenient configuration, measurement and documentation as well as simple sending of reports via connection to the testo 400

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Volume flow measurement at swirl outlets - the background

Problem for measuring hood volumetric flow at swirl outlets: air turbulence

Without an integrated flow straightener, the measurement result can be inaccurate by air turbulence.

Depending on how the flow hits the instrument, the flow velocities measured are either too high or too low.

Other measuring instruments for Ventilation and A/C professionals