This work is divided into two main parts, investigational and theoretical. The first part deals with the investigation of deposition values around integrated iron and steel works, and coke works, in South Wales, and with the changes in such values which arise as a result of modifications to process control or to arrestment equipment. A method of evaluation of such changes, based on the cumulative sum technique, is developed, which m1n1m1ses the effect of seasonal variations in the deposition values. It is demonstrated that there are two significant sources of particulate emission, from coke oven discharges, and from coke quenching. These are shown to have different spatial distributions, emissions from quench towers being very widespread, whereas emissions from oven discharges deposit relatively closer to the source. Methods to reduce both of these sources are described: It is shown that the use of arrestors in quench towers leads to enhanced emission of dissolved solids, but that the increase can be controlled by the use of additional sprays above the arrestors. The second part considers some theoretical aspects of quench tower operation. It is shown that the installation of arrestors leads to changes in gas temperature and gas composition in a quench tower, which cause increases in terminal settling velocity. The same changes lead to reduced condensation within the quench tower, and hence greater emission of steam, which gives a more buoyant emission, with more widespread dispersion than from open quench towers, as well as enhanced emissions of dissolved solids. Calculations are included which confirm the extent of the dispersion from towers fitted with arrestment devices.