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Inspect the modular-probe filter

Check the external probe filter when flow is weak.

Next-Gen testo 300

Applies to: Modular flue gas probe shown here; confirm its part number.

Before you start: Stop sampling and let the probe cool. Follow the manual’s condensate precautions.

Inspect the window

Look for contamination in the filter chamber.

Hands holding the modular flue gas probe for a Next-Gen testo 300 at its transparent particle-filter chamber.
Modular-probe chamber. Testo manual, page 89 ↗ · Select image to enlarge.

Replace when needed

Turn gently anticlockwise to open. Fit the specified filter plate, 0554 3385.

Lock the chamber

Turn clockwise to secure the chamber before further use.

If the issue continues: Persistent weak flow needs assessment. Include the probe and describe any hose damage in the service request.

Still need help with your device?

Include the model, serial number, exact error and checks already completed.

Start a service request

Source and applicability

Next-Gen testo 300 - Combustion Analyzer: Instruction Manual — §10.10, pp. 88–89. 0970 3010 en 07 - 11.2022

Open the complete Testo operating manual ↗ · Find this model in the manual list

QRM wording summarizes the checks. Diagram excerpts © Testo SE & Co. KGaA. Follow the complete manual and warnings for your instrument. Source checked 7 September 2026.