Abstract: A pressure isolation assembly can include multiple pressure isolation modules arranged in series and isolating a pressure actuated downhole tool from a downhole fluid pressure. Each of the modules may be configured to open in response to a single pressure cycle comprising an increase in the downhole fluid pressure followed by a decrease in the downhole fluid pressure. A method can include determining a number of fluid pressure cycles to apply to enable actuation of a downhole tool; installing a number of pressure isolation modules in a pressure isolation assembly, the number corresponding to the number of pressure cycles; deploying the downhole tool and the pressure isolation assembly while the pressure isolation assembly isolates a fluid passage of the downhole tool from downhole fluid pressure; and applying the number of pressure cycles, thereby permitting communication of at least a fraction of the downhole fluid pressure to the fluid passage.