About 2,500 officers in 16 forces were issued with the sprays at the beginning of March as part of a six-month trial. Police chiefs hoped they would help stem the rising number of injuries against officers sustained on duty.
Opponents of the spray have argued that it has dangerous side-effects and has not been properly tested.
In the first two months, sprays were used on 131 occasions and were drawn but not fired in another 174 incidents.
A report carried out for the Association of Chief Police Officers' (Acpo) self-defence sub-committee concludes that there has been a positive response from patrol officers to the incapacitant. It is understood that the study found no long-term medical problems from using the spray. In no case has a doctor needed to recommend further medical treatment beyond the initial aftercare. The report also says people are recovering from the effects of the CS within minutes, which the experts had predicted.
CS spray takes immediate effect and causes streaming to the eyes and nose, eyelids spasms, breathing difficulties, and in some cases blistering to the skin.
A final decision will be made at the end of the six-month trial, but police sources said chief constables were increasingly convinced the sprays should be adopted nationally. They have pointed to a growing number of incidents in which the spray, or the threat of it, has been useful in dealing with violent offenders.
An example occurred a week after the trials began. Police were called to a disturbance in which a 23-year-old man had barricaded himself into his room in Forest Gate, east London, after threatening his family with a chisel.
When police officers tried to talk to him he lunged at them with a spear before setting fire to his room. The officers used to spray to disarm him and get him out of the burning building. News that the police believe the sprays are a valuable addition to their armoury will cause concern to civil-liberty groups.
Early this month Liberty called for the trials to be halted after it accused the police of breaching the guidelines covering the use of the spray.
They highlighted two cases. One in March involved a man who died in police custody in east London after CS spray was squirted into his face although his arms were handcuffed behind his back.
However, the police have stressed that a post mortem found that Ibrahima Sey, 29, was suffering from heart disease. In the second case a group of nightclubbers is to sue the Merseyside police force after officers allegedly released CS spray into their coach, and then shut the doors. Liz Parratt, campaigns co-ordinator of Liberty, said: "We think it is therefore very difficult to describe the trials as a success."Reuse content