<em>Condemned</em> is an adjective derived from the verb <em>to condemn</em>. According to the Merriam-Webster Dictionary, it has several meanings:
declared to be reprehensible, wrong, or evil
pronounced guilty and sentenced to punishment (usually to death)
officially declared to be unfit for use
Since the sentence is about gas cylinders, a type of product, we can conclude that the third meaning is the correct one. Cylinders can't be declared wrong or evil or sentenced to punishment. They can be only declared unusable, which fits the context - gas cylinders that cannot be identified must be removed from service, declared unfit for use, and rendered incapable of holding pressure.
As a former slave, Frederick Douglass felt that education is the only way to break the chains of slavery. An educated man is free from ignorance and cannot be enslaved, so slaves should strive to get educated by any means possible.
