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 mustn't ventilate you mustn't ventilate she mustn't ventilate we mustn't ventilate you mustn't ventilate they mustn't ventilate
V-ing form
I mustn't be ventilating you mustn't be ventilating she mustn't be ventilating we mustn't be ventilating you mustn't be ventilating they mustn't be ventilating
Perfect
I mustn't have ventilated you mustn't have ventilated she mustn't have ventilated we mustn't have ventilated you mustn't have ventilated they mustn't have ventilated
V-ing perfect
I mustn't have been ventilating you mustn't have been ventilating she mustn't have been ventilating we mustn't have been ventilating you mustn't have been ventilating they mustn't 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
mustn't I ventilate? mustn't you ventilate? mustn't she ventilate? mustn't we ventilate? mustn't you ventilate? mustn't they ventilate?
V-ing form
mustn't I be ventilating? mustn't you be ventilating? mustn't she be ventilating? mustn't we be ventilating? mustn't you be ventilating? mustn't they be ventilating?
Perfect
mustn't I have ventilated? mustn't you have ventilated? mustn't she have ventilated? mustn't we have ventilated? mustn't you have ventilated? mustn't they have ventilated?
V-ing perfect
mustn't I have been ventilating? mustn't you have been ventilating? mustn't she have been ventilating? mustn't we have been ventilating? mustn't you have been ventilating? mustn't they have been ventilating?