Is it permissible for a woman to remain alone in a room with a non-mahram man to speak with him while she is wearing the niqab?

It is not permissible for a man and a non-mahram woman to be in seclusion (khalwa) together, due to the Prophet (peace and blessings of Allah be upon him) saying: "No man is alone with a woman unless there is a mahram with her," and his saying: "No man is alone with a woman except that Satan is the third of them." Scholars are unanimous on the prohibition of a man being in seclusion with a non-mahram woman. Seclusion is defined as being alone in a place where the man and woman feel secure from others observing them. This includes their being alone in a place where they converse privately, even if it is in plain sight of people, as long as their conversation cannot be overheard. Seclusion is removed by the presence of a mahram or a righteous woman. Therefore, if you need to meet the officer and do not have a mahram with you, let a righteous woman be with you during the meeting.