is that grammar correct?

The manager reviews these manuals regularly because the facilities and operation procedure will need to be updated from time to time.

There are no standard emergency procedures because different personnels are involved in different perspectives; therefore, we require staff with previous experience to handle the emergency procedures. If the situation is very dangerous and life threatening, the staff should contact and refer to the manager's final decision.

I hope I didn't change your meaning since I don't fully understands what you mean, such as the operation part or if the manual you are referring to is the emergency manual, at least it implies so. Hope that helps!

Manager review these manuals regularly because the facilities and the operational procedure can be changed. There is no standard emergency procedures because each condition and the people who are involved are different from time to time. The staff has to based on previous experience and own knowledge to handle each condition. If things become very dangerous, the staff should report the incident to the manager who can resolve the problem.

the manager review these manuals regularly because the facilities can be changed thus the operate manner will be changed. there are no emergency procedures because each of the condition and people involved are different. the staff will be based on his/her previous experience and knowledge in order to handle it. if the situation is highly dangerous, the staff should ask the manager to handle it.

都唔係幾知你講啲乜喎。係咪講工廠運作，同工業安全啲野呀？
because 之前無comma會唔會好啲呢？
because the facilies can be....去到can be changed.呢段唔知你想講乜
each of the conditions
their own knowledge
我都唔係好識。sorry

"Manager review(s) these manuals regularly because (new) facilities that operat(or) manuals can be changed.There (is) no emergency procedure( b)ecause each of condition and people of involvement are different. The staff need to base on p(re)vious experience and own knowledge to handle it. If the thing is very dangerous, the staff should tell the manager to handle it."

I quote from the upper one and I have made some more corrections.
What' more , plz correct my clumsy mistake if i have a wrong guide
to you.^_^

Manager review(s) these manuals regularly because (new) facilities that operat(or) manuals can be changed.There (is) no emergency procedur.Because each of condition and people of involvement are different. The staff need to base on pervious experience and own knowledge to handle it. If the thing is very dangerous, the staff should tell the manager to handle it.