Documenting CO Alarms: Tenants in Germany

As a tenant family in Germany, you should carefully record CO incidents and readings because they affect your safety and rights under tenancy law. This guide explains in clear language which information is important, how to document photos, timestamps and conversations with your landlord, which deadlines apply and when to send a formal defect notice. We show practical templates, examples of evidence and how to collect documents for possible rent reductions or legal steps at the local court. The goal is to help families in Germany act calmly, safely and legally prepared when a carbon monoxide alarm occurs.

Why documentation matters

Well-kept documentation helps to prove your claim for defect remediation or rent reduction and protects you if a case goes to the local court. The tenant obligations of the landlord are based on tenancy law in the BGB, especially the provisions on defects and maintenance.^[1]

What to record

• Photos and videos of the CO alarm and surroundings (photo, evidence) showing the measured values.
• Measurement logs or screenshots of the display (record, log) including the time.
• Correspondence with the landlord: defect notice and responses (notice).
• Date and time of alarms, calls and actions (deadline).
• Witnesses with full contact details for later statements.
• Repair reports or inspection protocols from qualified technicians.

How to send a defect notice

The defect notice (written notification of defects) is usually not an official numbered form; it must, however, be clearly described, dated and signed. Example wording: "I hereby notify a significant defect in the dwelling: CO alarm on [date, time]. Please inspect and remedy the defect immediately." Send the notice by registered mail or by email with read receipt and archive the proof of dispatch. Legal bases can be found in the BGB.^[1]

If the landlord does not react or the danger is not remedied, legal action may be necessary. To initiate a lawsuit, the complaint must be filed according to the rules of the ZPO; observe the procedural requirements in the ZPO.^[2] Cases are usually decided first by the local court; appeals can reach the Federal Court of Justice (BGH).^[3]

FAQ

Can I reduce the rent because of a CO problem?

Yes, in case of significant impairment tenants may be able to reduce the rent; document the defect carefully and inform the landlord in writing.^[1]

Who decides on a dispute about rent reduction?

The local court decides in the first instance; in higher instances the case can go to the BGH.^[3]

Which deadlines apply if the landlord does not respond?

For legal actions the rules of the ZPO apply; check deadlines and formal requirements before filing.^[2]

How-To

1. Photograph the alarm display and the surroundings immediately with a timestamp.
2. Send a written defect notice to the landlord and keep proof of delivery.
3. Contact emergency services in case of immediate danger and note names and reference numbers.
4. Have measurements and repairs recorded by qualified personnel.
5. Prepare documents for the local court if you need to take legal action.

Help and Support

• BGB §535 ff. — Bürgerliches Gesetzbuch
• ZPO — Zivilprozessordnung
• Umweltbundesamt — Information on indoor air

1. [1] Bürgerliches Gesetzbuch (BGB) §535 ff. — gesetze-im-internet.de
2. [2] Zivilprozessordnung (ZPO) — gesetze-im-internet.de
3. [3] Justiz portal of German courts — justiz.de