Hilase Ltd. introduces WaSul-Hygro, which is a fully automatically operated, industrial laser based water vapor professional monitoring system. It has a very wide measurement range (from 0.3 ppm. up to 25000 ppm.) and its response time is about a few seconds. It can measure water vapor in up to 3 independent gas streams. WaSul-Hygro can be operated under harsh conditions. Measured water vapor concentration can be stored in the system’s internal professional memory for a measurement period of about two months, or can be transferred to a PC or to a data logger through RS232/RS485, Modbus, or 4-20 mA. It can be supplemented with an additional laser for measuring other gas components (methane, ethane, oxygen, ammonia etc) as well. One WaSul-Hygro system is operated on-board of a passenger aircraft within the CARIBIC project (www.caribic-atmospheric.com ) since May 2005, and successfully completed more than 30 flight campaign. Other WaSul systems are operated e.g. in natural gas plants. The expected trouble free operational lifetime of a WaSul-Hygro system exceeds ten years. Each WaSul-Hygro system is delivered with a certificate of calibration, which is issued by an accredited calibration laboratory.