Back in the 1960s and 1970s, a ceiling wasn't considered dressed properly without a neat covering of polystyrene tiles. Expanded Polystyrene (EPS) tiles were modern, warm, soundproofing and cheap. Unfortunately, they are a fire hazard, as they will melt and drip, potentially causing horrible burns and exuding carcinogenic fumes. They also turn yellow with age and lift away from the ceiling making a room look outdated and shabby. If you still have any polystyrene tiled ceilings, now would be a good time to get rid of them.
You will need a step-ladder or builder's platform, flat bladed scrapers and a paint stripper heat gun. It is a good idea to have several scrapers of varying sizes and angles. Some will work better than others in certain areas. Have plenty of black bin liners to hand for the clear-up afterwards. A suitable filler to repair any minor damage to the ceiling is a good idea.
Polystyrene safety precautions
Polystyrene tiles are not hazardous to health in their normal state but the removal of the adhesive may be. As you cannot tell which adhesive was used, it is wise to take some precautions. In most cases you will be working above your head, so wear safety goggles and head protection. When removing the adhesive, you will need heavy-duty rubber gloves to shield your hands from the heat gun. Remove the furniture from the room or cover it carefully with plastic sheeting.
Begin levering off the tiles with a scraper. You should be able to lift one edge and simply crack the tiles off. If you are lucky, the adhesive will come away with the tile. When you have removed all the tiles, use the heat gun to melt any remaining adhesive and scrape it off. Avoid digging the scraper into the plaster accidentally.
Clearing and disposal
Wash the ceiling with warm soapy water and check for damage. Repair any cracks or holes as necessary. In extreme cases the ceiling may require re-plastering. If it is possible, place the tiles in bags separate from the scraped-off adhesive.
Contact your local council regarding the disposal of polystyrene tiles -- it is unlikely that they will be picked up during the routine rubbish collection. You can either take them to the waste facility or arrange for the council to collect them. If the tiles are relatively free of adhesive, they can be recycled. If you, or your neighbours, do a lot of gardening then the old tiles can be used in the bottom of pots and containers as drainage and insulation.