I must ventilate you must ventilate she must ventilate we must ventilate you must ventilate they must ventilate
V-ing form
I must be ventilating you must be ventilating she must be ventilating we must be ventilating you must be ventilating they must be ventilating
Perfect
I must have ventilated you must have ventilated she must have ventilated we must have ventilated you must have ventilated they must have ventilated
V-ing perfect
I must have been ventilating you must have been ventilating she must have been ventilating we must have been ventilating you must have been ventilating they must have been ventilating
Negation
Simple form
I must not ventilate you must not ventilate she must not ventilate we must not ventilate you must not ventilate they must not ventilate
V-ing form
I must not be ventilating you must not be ventilating she must not be ventilating we must not be ventilating you must not be ventilating they must not be ventilating
Perfect
I must not have ventilated you must not have ventilated she must not have ventilated we must not have ventilated you must not have ventilated they must not have ventilated
V-ing perfect
I must not have been ventilating you must not have been ventilating she must not have been ventilating we must not have been ventilating you must not have been ventilating they must not have been ventilating
Interrogative form
Simple form
must I ventilate? must you ventilate? must she ventilate? must we ventilate? must you ventilate? must they ventilate?
V-ing form
must I be ventilating? must you be ventilating? must she be ventilating? must we be ventilating? must you be ventilating? must they be ventilating?
Perfect
must I have ventilated? must you have ventilated? must she have ventilated? must we have ventilated? must you have ventilated? must they have ventilated?
V-ing perfect
must I have been ventilating? must you have been ventilating? must she have been ventilating? must we have been ventilating? must you have been ventilating? must they have been ventilating?
Interro-negative form
Simple form
must I not ventilate? must you not ventilate? must she not ventilate? must we not ventilate? must you not ventilate? must they not ventilate?
V-ing form
must I not be ventilating? must you not be ventilating? must she not be ventilating? must we not be ventilating? must you not be ventilating? must they not be ventilating?
Perfect
must I not have ventilated? must you not have ventilated? must she not have ventilated? must we not have ventilated? must you not have ventilated? must they not have ventilated?
V-ing perfect
must I not have been ventilating? must you not have been ventilating? must she not have been ventilating? must we not have been ventilating? must you not have been ventilating? must they not have been ventilating?