Table 1 In - and exclusion criteria

1. Written informed consent from the parents or custodians of the study participant.

1. Suspected or proven meningitis or encephalitis as a possible cause for a past cerebral seizure associated with fever.

2. At least one febrile seizure in the past medical history of the study participant.

2. Presence of a neurological disease or a brain malformation.

3. Age 12 months—5 years in phase 1 and age 6 months—5 years in phase 2 of the adaptive design (after observation of 20 seizures, approximately patients number 81-288).

4. Cerebral seizures without fever in the past medical history.

5. Proof of spike-wave discharges or of a focus in the in the interval EEG.

6. Presence of a respiratory illness (e.g. bronchial asthma or bronchopulmonary dysplasia, BPD).

7. Presence of other severe organ or chronic diseases.

8. Current participation in another clinical trial.

9. Failure to provide written informed consent on part of the parents or custodians with regard to the storage and dissemination of pseudonymized study results.

10. Known adverse reactions against carbogen.

11. Placement of either the child or a parent/custodian in an institution, based on judicial orders.

12. Lack of understanding of the study procedures on part of the parents or custodians (e.g. lack of language knowledge or of general intellectual capacity).