Ultra-Low Pressure switches has all-welded construction which eliminates leaks. It has accurate low pressure switching ranges from 300″ H2O to 250″ H2O. They're ideal for monitoring furnace drafts, tank- blanketing combustible liquids, dryers and blowers in corrosive atmospheres, and low gas flow purge lines. This switch has unlimited uses, for example it can be used to detect a forced entry into a building. All that is necessary is to have a small blower pressurize the building, and obtain an outside reference pressure as close as possible to the blower intake. Opening a window three inches will cause an immediate pressure drop to actuate the switch. It can also be used as a low cost backup for clean rooms, indicating the loss of pressure or dirty air filters. The fact that it is capable of operating on extremely low pressure with an accuracy of 1% of full scale for -40°F to +120°F makes it very useful for crucial applications.