Regarding Article 2.2.3 of GB50058

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“II. Primary release sources: Sources that are expected to release substances on a periodic basis or occasionally during normal operation. Cases similar to the following can be classified as first-level release sources: 1. Seals of pumps, compressors, valves, etc., which release flammable substances during normal operation ； 2. During normal operation, flammable substances are released into the space; the drainage system installed on containers holding flammable liquids ； 3. Sampling points that release flammable substances into space during normal operation. III. Secondary release sources: Sources that are not expected to release under normal operation, and if they do release, it is only on an occasional and short-term basis. Cases similar to the following can be classified as second-level release sources: 1. Seals of pumps, compressors, and valves that should not release flammable substances during normal operation ； 2. Flanges, connectors, and pipe joints that cannot release flammable materials during normal operation ； 3. At normal operation, at safety valves, exhaust ports, and other openings that should not release flammable substances into the space ； 4. Sampling points from which flammable substances cannot be released into space during normal operation. ” ----------------------- The above is the original text. What I want to ask is: under the same normal operating conditions, why do some devices release flammable substances while others do not?