VEERASWAMI, C.J.

In these two tax cases, the question presented is whether spray booths, dust collectors and textile humidification plants are air-conditioners within the meaning of entry 4 of the First Schedule to the Madras General Sales Tax Act, 1959. That entry is : Refrigerators, air-conditioning plants, component parts of refrigerators or air-conditioning plants. On such goods, the rate of tax levied on their sales is 12 per cent., and the levy is at the point of first sale in the State. The Tribunal has held that these articles are not within the purview of the entry.

In respect of the first two, namely, spray booths and dust collectors, we are clearly of opinion that they are not air-conditioners. The spray booth is intended for component painting in the engineering industry. The spray booth comprises of a collecting section and a booth section. The former may be used separately as a paint-mist collector in a spray shop or in combination with one or two booth sections in sequence. The paint-mist collector uses a closed-cycle water system, a suitable paint neutraliser being added. From a channel at the top of the booth, the water runs in an even film down the screen wall to the venturi throat, where it is atomized by the inducted air. The minute water droplets enclose the paint particles and drop into a tank below, where the paint forms an easily skimmed surface layer. Entrained water droplets are removed from the cleaned air in the dewatering section, and the air is exhausted by a fan to the atmosphere. This fan, preferably of sparkproof construction, is located at any suitable position and connected to the booth by ducting. The booth sections are equipped with tubular lighting at the roof. Dust collectors are used in modern industries, which have created severe problems of air pollution. It has been found necessary to limit the emission of dust into atmosphere as far as possible in order to minimise the health hazard as well as damages to machinery, crops etc. It is in this connection well-planned plants with good dust collectors are found essential. Dust collectors are also used for gas cleaning, for recovery of valuable dust and as final collectors for pneumatic conveyors. There are four main types of industrial dust collectors, namely, dynamic collectors based on forces of inertia, wet collectors based on agglomeration with water, fabric filters based on the screening effect of a textile material, and electric precipitators based on electrostatic forces. In designing the dust collector plants are taken into consideration the factors like the plant or process in which the dust collector is to be installed, the nature of the gas, the temperature and humidity of the gas, the chemical and physical properties of the dust and dust concentration in the gas and the collecting efficiency required. In some cases, only one particular type of dust collector is suitable, in other cases, different types are possible. The choice will be a compromise considering the collecting efficiency, resistance to wear, the space available, installation cost, operational cost etc. Textile humidification plants are an integral part of the Indian textile industry and it is stated that at present more than 3/4 of all mills are equipped with SF plants. An SF textile humidification plant consists mainly of a number of humidification towers, duct system and high efficiency distributors. The towers which are suitably placed, vary in size and number and are correctly designed from the standpoint of air technology to suit each particular application. A stream line axial flow fan turns outside air, returns air or a mixture of both into a tower through screened inlets. On the pressure side of the fan, the air flow is reduced in a diffuser and then passed through a spray washer, lowering the dry pulp temperature and giving a marked cooling effect known as evaporative cooling. A fan of type PMA is specially designed for humidification towers and