Safety system and method for constructing air conditioning system

A safety system comprising:

• a plurality of valve units in a heat pump system, each of the valve units having
• at least one liquid refrigerant pipe portion,
• at least one gas refrigerant pipe portion,
• at least one liquid control valve disposed in the liquid refrigerant pipe portion,
• at least one gas control valve disposed in the gas refrigerant pipe portion,
• a casing accommodating at least the liquid control valve and the gas control valve and formed with at least two openings, and
• a refrigerant leakage sensor configured to detect an occurrence of a refrigerant leakage in an internal space of the casing;
• a connection structure comprising a plurality of individual ducts connecting the internal spaces of the casings via the openings;
• and
• a discharge structure connected to the connection structure or one of the casings,
• and configured to discharge air from the internal space of the casing in which a refrigerant leakage has occurred, wherein
• the casing of each valve units has first and second lateral faces facing different directions, and
• in each of the valve units, a first opening as one of the openings is formed in the first lateral face and a second opening as another one of the openings is formed in the second lateral face.