The control of microbial load on surfaces of research and animal labs as well as of hospital and production rooms is an everyday challenge. Surface sanitization or disinfection of production equipment’s and rooms by wiping with chemicals is a time-consuming procedure. Its validation is very intricate. Alternatively, fumigation allows overcoming many critical aspects of wiping in both procedure and validation. Moreover, the use of nebulized hydrogen peroxide (H2O2) of moderate concentration resolves remaining reservations as to toxicity, corrosion, and persistence. The new concept has been applied to the decontamination of small rooms as well as to large multi-rooms up to 750 m³. These are described and illustrate the wide field of application of the technique proposed. The concept presented for validation of the sanitization procedure overcomes the problems associated with conventional surface disinfection validation. It allows for considerable more safety at greatly reduced cost and work.