testo 420 - Air Flow Hood 

Order-Nr.  0563 4200

$5 026.00
incl. GST $5 528.60
  • 16 measurement points that records Temperature, Humidity, Differential & Absolute Pressure. 

  • Highly precise readings at swirl outlets thanks to flow straightener. 

  • IOS & Andriod App Integration via Bluetooth connectivity. 

  • Onsite report generation & email. 

The Testo 420 volume flow hood is suited for HVAC systems and comes with a control panel for displaying measurement data. The control panel can be tilted or removed to suit user requirement. 

testo Smart-App

The App for all applications. Multifunctional. Continuously up to date. Free.

Find out more

Air balancing – time saving up to 30%

New PRO measuring program in the testo Smart App

Find out more


Volume flow hood weighing less than 2.9 kg


Product Description

The Testo 420 measuring instrument enables you to measure flow velocity, volume flow, absolute pressure, temperature and relative humidity. The automatic zeroing function ensures higher accuracy for low pressures.

All measuring values are easy to read on the large display which has an illumination function. For analysis and documentation, measurement data can be saved and measurement protocols can be created directly on site using the testo 420 App. In addition the measurement data can be easily accessed via PC without any additional software thanks to the plug & play function.

The Testo 420 volume flow hood with its integrated measuring instrument was not only developed to measure volume flow measurement. The measuring instrument can also be taken off the hood and used to measure pressure, flow and volume flow measurements in a duct. Simply attach a Pitot tube and connection hoses (both optional). With integrated, timed and multi-point mean calculation.

High measuring accuracy at swirl outlets thanks to volume flow straightener

Volume air flow is frequently measured at swirl outlets. Air flows are often incorrectly measured due to the turbulent air at these outlets.

The Testo 420 enables you to significantly reduce these measurement errors. The integrated volume flow straightener calms the turbulence and converts it into a virtually uniform air flow. This enables accurate calculation of volume flow in the 80 to 3,500 m3/h range.

Create protocols directly on site and E mail them using the Testo 420 App

Take advantage of further practical functions and download our free App. Because the App connection enables mobile devices such as smartphones and tablets to be used as a secondary display and as a remote control via Bluetooth.

The App enables live measurement on HVAC systems using a start and stop function and the saving of measurement data in txt format. You can create the measurement protocol directly on site using the App. Measurement results, such as the overall volume flow and the air exchange rate, can be directly assigned to customer-specific protocol templates. You can then send your readings and protocols via the e-mail function. This means you save a considerable amount of time and increase efficiency. 

Delivery Scope

testo 420 volume flow hood including measuring instrument, 610 x 610 mm hood, 5 x tension rods, USB cable, batteries, trolley and protocol certificate.

Technical Data

Temperature - NTC

Measuring range

-20 to +60 °C


±0.5 °C (0 to +60 °C)

±0.8 °C (-20 to +0 °C)


0.1 °C

Reaction time

45 s (t₉₀)

Humidity - Capacitive

Measuring range

0 to 100 %RH


±1.8 %RH + 3 % of mv at +25 °C

(5 to 80 %RH)


0.1 %RH

Differential Pressure - Piezoresistive

Measuring range

-120 to +120 Pa


±2 % of mv + 0.5 Pa at +22 °C, 1013 hPa


0.001 Pa

Reaction time

1 s (t₉₀)

Absolute Pressure

Measuring range

700 to 1100 hPa


±3 hPa


0.1 hPa

Reaction time

1 s

Volume flow

Measuring range

50 to 4000 m³/h


±3 % of mv + 12 m³/h at +22 °C

1013 hPa (85 to 3500 m³/h)

Reaction time

1 s (t₉₀)


1 m³/h

General technical data


2900 g


610 x 610 mm (Standard hood)

Operating temperature

-5 to +50 °C

System requirements

requires iOS 12.0 or newer; requires Android 6.0 or newer; requires mobile end device with Bluetooth 4.0


EU-guideline 2014/30/EU

Battery type

Alkali manganese, mignon, type AA

Battery life

40 h

Display size


Display function

Dot matrix

Display ligthing

with illumination


Micro-USB; Bluetooth® 4.0 wireless technology

Data transfer


Radio range

10 m


2 GB (internal)

Storage temperature

-20 to +60 °C



incl. GST  $481.80
incl. GST  $555.50
incl. GST  $555.50
incl. GST  $908.60

Additional accessories and Spare parts

incl. GST  $106.70
incl. GST  $106.70
incl. GST  $316.80
incl. GST  $280.50
incl. GST  $788.70

$5 026.00
incl. GST $5 528.60