A pressure cooker is the clearest image of tension held in, and dream books read it as stress building under a sealed lid. Its steam valve stands for the need to let some of it out safely.
Does the traditional reading fit your dream, or did it mean something else to you?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.