HOWEVER attractively laid out a housing estate may be, it is almost impossible at present to avoid the problems of smell, unhygienic litter and vermin associated with the disposal of refuse. Some apartment blocks close to the refuse collection area suffer more than others, but, in general, it is a problem which affects everyone on the estate. However, the Housing Authority is aware of the problem and is planning to test two Automated Refuse Systems which could change all this. The first, which will be installed at Fanling 47B Phase 1 estate, will be tested initially in three blocks. The pilot scheme will use a Swedish system manufactured by AB Centralsug. It will cost $12.8 million and will begin trials in August 1995 when the construction of the buildings is complete. The principle is quite simple. Bagged refuse is tipped into the rubbish chute in each building, but instead of dropping directly into the wheeled refuse bin presently in use, it joins an underground network of pipes. This section drags the bags to an undercover refuse collection centre where they are compacted into containers and removed by vehicles. The whole system is either under cover, or underground, which keeps smell, litter and other problems away from the general public. A similar system, the American Trans-Vac, will undergo trials in Phase 1 of Shek Yam estate starting in January 1996. Tenants will not have access to the chutes in the buildings; the cleansing contractor will dump the refuse which will avoid the occasional inappropriate object blocking the system, even though the makers claim that almost anything will be sucked through the pipes. ''The system will provide considerable environmental improvement, and the refuse vehicle will not need to approach each building as it does now,'' said acting senior architect Ken Bothick. ''This will improve safely conditions for residents. ''It is likely that there will be financial savings in the long run in provision of refuse bins and reduction of staff.'' But Mr Bothick said there would be the capital installation costs, and the urban services would need to purchase new vehicles to remove the containers. If the trials were satisfactory then it was possible that these systems would be introduced throughout Housing Authority estates.