=Approval of Plans.=--There are many points in building construction to take care of in the matter of design, to meet the requirements of the insurance interests and local city building department regulations, which in the main coincide. Before entering into a contract to construct, it is well to have the drawings approved by the insurance boards and the city inspection bureau. It obviates expensive changes and additions. To build in such a manner as to bring the insurance rates to a minimum is certainly desirable. It is an advantage, too, to have the plant divided so that in case of fire the spread of the flames can be retarded and the fire confined to the building where it originated, or if some of the buildings are burned the balance can be saved. Fires invariably represent, to a well managed business, a far greater loss than is collectible on the insurance policies. CHAPTER IV REFRIGERATION EQUIPMENT AMMONIA MACHINES -- AMMONIA -- COMPRESSOR -- CONDENSER -- RECEIVER -- COOLER -- CONDENSING WATER -- UNIT BASIS -- COMPUTING FROM UNIT BASIS -- HOW RATED -- FREEZER REQUIREMENTS -- FREEZERS IN SMALL PLANTS -- CYLINDER ARRANGEMENT -- WHY BRINE CIRCULATION -- AIR CIRCULATING -- FORCE DRAFT -- COIL ROOM SYSTEMS -- BRINE CHILLING -- BRINE METHODS -- TYPES OF BRINE COOLERS -- BALANCED BRINE SYSTEM -- DIRECT EXPANSION -- TWO-STAGE COMPRESSORS. =Mechanical Refrigerating Equipment.=--This agent is of great consequence in the operation of packing houses, and, therefore, it is deemed essential to explain the principles briefly; as well as to describe the uses. =Ammonia Machines.=--The use of ammonia refrigeration equipment either absorption or compression has so generally displaced all others for stationary or land use, and particularly in meat plants and cold storage houses, that for the present purpose it is unnecessary to go into a discussion of others. The compression system being so predominant in its use, a description of same is given. The diagram indicates a compression system in elementary form consisting of: (1) A pump or compressor which withdraws the gas from the cooler or expansion tank, prepares and passes it to the condenser. (2) The condenser or liquifier which gives to the water flowing over it the heat carried to it by the gas from the cooler. (3) The cooler or expansion tank in which the heat extracted from the carcasses, the building walls or elsewhere, is passed to the ammonia gas for conveyance to the condenser.