THE Fire Services Department is to step up spot checks on fire extinguishers at the Hongkong Polytechnic following allegations that more than 250 of them do not work properly. Fire officers are expected to contact the campus security department later this month after a claim in an internal paper that 60 per cent of the 425 extinguishers in the Chung Sze Yuen Building and newly-opened Block Phase III B are ''not in efficient working order''. There are about 1,200 fire extinguishers on the campus. All were checked by the contractor, Gold Banner Construction and Development Company, two months ago. Gold Banner dismissed the claims, made by a campus safety and fire officer, but said the polytechnic had complained about the devices having minor defects. A company spokesman said: ''We are a registered contractor. It is impossible that the fire extinguishers we have checked are not working. ''The polytechnic had asked us to remove the rust on some fire extinguishers and we completed the work in February.'' The Fire Services Department also doubted if an untrained campus officer could judge from the appearance whether a fire extinguisher could work properly or not. The department has received no complaints about fire service devices in other schools but says it will investigate the issue and step up checks at the polytechnic. According to fire regulations, the owner of any fire service installation is subject to a maximum fine of $5,000 if the devices are found not to be in good working order. The contractor is also liable to the same penalty. A spokesman for the polytechnic's estate service office claimed the internal paper was referring only to the cleanliness of the devices.