Reference Clauses of the Act : Art. 2, item (iii) and Art. 48, para. (4)
In a broad sense, all varieties of liquid can be called liquefied gas. In the Act, “liquefied gas” means a substance turning into liquid by artificially compressing or/and cooling that substance which is in a gaseous state at room temperature under normal pressure. However, in the High Pressure Gas Safety Act, “liquefied petroleum gas” means petroleum gas in both gaseous and liquid states.
In the Circular Notice, “liquefied gas” is defined as actual liquid falling under any of the following items:
(i) liquid whose boiling point (which means a temperature at which the liquid’s vapor pressure is equal to atmospheric pressure, regardless of whether the liquid is a pure substance or a mixture; the same applies hereinafter) is not more than 40 degrees Celsius under atmospheric pressure; or
(ii) liquid whose boiling point is more than 40 degrees Celsius under atmospheric pressure when it is in a state of being at not less than its boiling point and at not less than 1 MPa.
Note: Interim measures are prescribed regarding item (i) in the Circular Notice as amended in July 2011 and regarding item (ii) in the Circular Notice as amended in November 2016.
Whether a gas is a liquefied gas or compressed gas depends on its current state, irrespective of the variety of the gas.
Therefore, even when a gas with a low boiling point is often handled as a compressed gas in general, if that gas is artificially liquefied and in a liquid state, the gas is a liquefied gas.
In addition, a gas of the gas phase which is filled in a container with a liquefied gas shall be handled as a liquefied gas.
ref. High pressure gas and compressed gas