Mixed sensor varieties build total defense. Combine optical smoke alarms for residing areas with heat alarms for kitchens, all linked as a result of radio signals for unified fire detection. Blend: As being the name implies, this is a smoke detector that makes use of both photoelectric and ionization ways. https://www.thesafetycentre.co.uk/blog/ems-wireless-firecell-systems-from-the-safety-centre/