Testo 420 - Air Flow Capture Hood

Brand: Testo

The CEC compliant Testo 420 air flow capture hood with Bluetooth is the accurate, lightweight, and convenient solution for measuring volume flows at supplies and returns.

Handling this air flow capture hood with its flow straightener and tiltable display is especially easy, with its low weight of less than 6.4 lbs, 24" x 24" included hood dimensions, and ergonomic handles.

The rugged and durable Testo 420 air flow capture hood is an accurate and lightweight air flow instrument.
  • The hood features a unique flow straightener, which significantly improves measurement accuracy, saving you valuable time on difficult tasks
  • The Testo 420 control unit can be tilted for a more convenient view of the display
  • The included Bluetooth / app feature allows for wireless connection to mobile devices, for remote monitoring, as well as remote operation
  • The Testo 420 app can send measurement reports directly from the work site via email
  • For additional convenience, there is an optional tripod when working with high ceilings, as well as four additional flow hood sizes available for complete versatility
  • The Testo 420 is also a CEC approved air flow capture hood
  • Live data feed integration now available with the MeasureQuick App

The Testo 420 air flow capture hood is ideal for larger air supplies and returns, and enables fast and precise testing and balancing of indoor environmental systems.

It provides reliable data with precise calculations of the overall volume flow in HVAC systems.

Volume flow is frequently measured at swirl outlets, and airflow measurements are often incorrectly measured due to the turbulent air from these outlets.

Thanks to Testo’s volume flow straightener, you can be confident in receiving high measuring accuracy at swirl outlets.

The integrated volume flow straightener calms this turbulence and converts it into a virtually uniform air flow.

This enables highly accurate calculations of volume flow in the 24 to 2,354 CFM range.

Exceptionally Light

The Testo 420 air flow capture hood with ergonomic handles and tiltable display has an exceptional light weight of less than 6.4 lbs.

This means that frequent volume flow calculations in large rooms and measurements above head height can be carried out reliably and comfortably.

While in use, a large measuring button on the capture hood ensures easy recording of the measurements.

Removable Control Unit

The control unit of the Testo 420 enables you to measure flow velocity, volume flow, absolute pressure, temperature, and relative humidity.

The automatic zeroing ensures higher accuracy for low pressures.

This integrated measuring control unit was not just developed for volume flow measurement at ceiling outlets, as it can be removed from the capture hood and be used for pressure, flow, and volume flow measurements in the duct.

You only need to attach a pitot tube and connection hoses (both optional) for measurements in ducts.

Timed and multi-point mean calculation, as well as the combination of the two, together with simple input of the duct geometry, provide you with accurate flow measurements in ducts.

This means you can save on the purchase of an additional measuring instrument.

Testo 420 App

The Testo 420 app enables live measurement streaming of HVAC systems using a smartphone or tablet.

The app features a start and stop function and enables you to save your measurement data in .txt format, and creates the measurement protocol directly on site.

Measurement results, such as the overall volume flow and the air exchange rate, can be directly assigned to customer-specific folder templates.

You can then send your readings and protocols via the in-app email function, saving you a considerable amount of time and increasing efficiency.
  • Volume flow hood weighing less than 6.4 lbs
  • Volume flow hood for larger swirl outlets for measuring volume flow, temperature and relative humidity
  • Volume flow straightener for precise measurements at swirl outlets
  • Smartphone/tablet as a second display per App
  • App for creating on-site reports
  • Tripod for measurements up to a ceiling height of 4 m



Delivery Scope

  • 0563 4200 – Testo 420 Air Flow Capture Hood Base with Bluetooth, 24" x 24" capture hood with flow Straightener, USB Cable, Batteries, and Soft Case with Telescoping Handle and Wheels
  • 400563 4200 – Testo 420 Air Flow Capture Hood Base with Bluetooth, 24" x 24" capture hood with flow Straightener, USB Cable, Batteries, Soft Case with Telescoping Handle and Wheels, and NIST Certificate

Temperature - NTC

  • Measuring Range: -4°F to 158°F / -20°C to +70°C
  • Accuracy: ±1°F (32°F to 158°F) / ±0.5°C (0°C to +70°C) | ±1.4°F (-4°F to 32°F) / ±0.8°C (-20°C to +0°C)
  • Resolution: 0.1°F / 0.1°C
  • Reaction Time: 45 sec (t90)

Humidity - Capacitive

  • Measuring Range: 0 to 100 %RH
  • Accuracy: ±1.8 %RH + 3 % of mv at +77°F / ±1.8 %RH + 3 % of mv at +25°C (5 to 80 %rH)
  • Resolution: 0.1 %RH

Differential Pressure

  • Measuring Range: -0.480 to 0.480 inH₂O / -120 to +120 Pa
  • Accuracy: ±2 % of mv + 0.002 inH₂O at +72°F, 405 inH₂O / ±2 % of mv + 0.5 Pa at +22°C, 1013 hPa
  • Resolution: 0.001 inH₂O / 0.001 Pa
  • Reaction Time: 1 sec (t90)

Absolute Pressure

  • Measuring Range: 280 to 440 inH₂O / 700 to 1100 hPa
  • Accuracy: ±1 inH₂O / ±3 hPa
  • Resolution: 0.1 inH₂O / 0.1 hPa
  • Reaction Time: 1 sec

Volume Flow

  • Measuring Range: 24 to 2354 CFM / 40 to 4000 m³/h
  • Accuracy: ±3 % of mv + 7 CFM at +72°F / ±3 % of mv + 12 m³/h at +22°C | 405 inH₂O (50 to 2060 CFM) / 1013 hPa (85 to 3500 m³/h)
  • Resolution: 1 CFM / 1 m³/h
  • Reaction Time: 1 sec (t90)


  • 102 oz. / 2900 g


  • 24 x 24 in. (Standard hood) / 610 x 610 mm (Standard hood)

Operating Temperature

  • 23°F to 122°F / -5°C 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

  • Alkaline, type AA

Battery Life

  • 40 h

Display Size

  • 3.5"

Display Function

  • Dot Matrix

Display Lighting

  • with illumination


  • Micro-USB
  • Bluetooth® 4.0 Wireless Technology

Data Transfer

  • Bluetooth®

Radio Range

  • 32.808 ft. / 10 m


  • 2 GB (Internal)

Storage Temperature

  • -4°F to 140°F / -20°C to +60°C
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