The invention provides a monitor for measuring blood pressure and other vital signs from a patient without using a cuff. 1 to 3 weight % of one kind or more of a coloring agent, an antioxidant and a fragrance. It is preferred that the apparatus also includes a control means adapted to receive information as to the location of the target volume, and, on the basis of that information, control the longitudinal positions of the leaves and the lateral position of the support. The position member has a sleeve fitting and turning around the ball joint, and ratchet teeth provided on top. Thus, the foldable tent of the present invention is provided with secure and continuous ventilation, and is opened and folded without requiring additional assembly of components. The invention further relates to the use of the trichlorosilane so purified in the production of silane andor super-pure silicon.