SCP Foundation

Replacement of the chamber for quarantining SCP-XXXX infected subjects were shifted to Basement-4 level sector B73, located within Site 17.

I think you mean "was" not "were" but this sentence looks like it belongs somewhere else, to be honest. People typically start with something like "SCP-X must be contained in/surrounded by a secure locker/containment cell/perimeter fence."

Those who caused the breach due to their poor handling and improper procedure will be barred from operating any further SCPs.

This isn't a containment procedure and doesn't belong in the containment procedures.

Personnel in Site-17 at the time of quarantine are deemed killed in action, and no attempt to recover them is to be made.

I feel like this SCP belongs in its own separate site if we're just going to decide everyone is dead when things go wrong.

Unequipped staffs and personnel within Site 17 is discouraged to go down the basement level without any protective clothing.

You already said people are mandated to wear protective clothing. This is redundant, delete it.

Should anyone gets infected, medical assistants should wear protective clothing and bring the victim directly into SCP-XXXX chamber.

It's "Should anyone get" not "gets"
Also, why would you make people go into the chamber where, presumably, someone just got infected? Put them in a quarantine room.

Please do take note that only staffs or personnel with level 4 clearance are qualified for interaction with SCP-XXXX.

Redundant with previous sentences. Delete it.

Within 17 minutes, symptoms continue to perceive while new aggravated signs appeared.

I don't know what you're trying to say here.