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.
The fact that each unit is calibrated to primary standards makes a low cost way to find what a factory set value should be for future quantity purchases.