The above is good advice. You specifically mention you want to look after your health so even though the Nova is pretty self-contained the chemicals still give off some fumes (albeit low, some people are more sensitive to it than others). In the UK recommendations are for 10-15 air changes per hour. This is no different than the requirements for a domestic kitchen. May be different in Austria and your room size and facilities may vary.
People will say you don't need ventilation, or the above is over the top, but it makes for a better working environment and long term is better for your health.
A few links:-

Air changes per hour guidelines (UK)
Darkroom Fans Vent-Axia
B+H darkroom ventilation