Expressed in units of pounds/square inch (psi) or bar for membranes.


Measure of the amount of air pressure required to force liquid from the largest wetted pore of a membrane. Serves as an index of pore size and rates the filter's ability to serve as a particle barrier.

The bubble point is dependent on the liquid used to wet the membrane; for a given pore size, the bubble point will be higher in a liquid surface tension (such as water) than in a liquid with a lower surface tension (such as isopropyl alcohol). The bubble point rating is determined when the largest pore yields a bubble; the larger the pore, the less pressure required to form the bubble.

Expressed in units of pounds/square inch (psi) or bar for membranes.