The Testo 405 is a compact and reliable hot wire thermo‑anemometer designed for fast, accurate measurement of air velocity, volume flow, and temperature. Its sensitive hot wire sensor captures low air movements, making it ideal for detecting leaks around windows and doors, as well as for routine HVAC duct measurements.

The instrument features a telescopic probe that extends to reach inconvenient spots, while the sensor head can be adjusted and rotated for optimal alignment with airflow. A large, backlit LCD display rotates 180°, ensuring clear readings from any angle. Operation is simplified with a single‑button interface, making the 405 exceptionally easy to use in the field.

Measurement ranges cover air velocity from 0 to 10 m/s, volume flow up to 99,990 m³/h, and temperature from -20°C to 50°C. The device ships complete with a duct holder, belt clip, and battery, ready for immediate use.

Typical applications include:

• HVAC system balancing and troubleshooting
• Verification of air flow in ducts and vents
• Detection of drafts around windows, doors, and building envelopes
• General indoor air quality and ventilation assessments

Features

• Hot wire technology for accurate low‑velocity measurement
• Air velocity range: 0 to 10 m/s
• Air volume range: up to 99,990 m³/h
• Temperature range: -20°C to 50°C
• Telescopic probe with adjustable, rotating sensor
• 180° rotatable large LCD display
• One‑button operation for simplicity
• Includes duct holder, belt clip, and battery
• Metric units only