Fire union chiefs in South Yorkshire said more strikes are likely following two periods of industrial action.
Contingency crews with minimal training were called out to seven incidents while operating a reduced emergency response unit on Friday night.
The calls came as firefighters from South Yorkshire Fire and Rescue Service walked out for five-and-a-half hours in a dispute over pensions.
Picket lines were set up at stations in Sheffield, Doncaster and Barnsley and demonstrations also took place.
A warning was issued ahead of the strike, which took place during the typically busy period between Halloween and bonfire night, urging people to put off firework displays or attend organised events.
Another strike organised by the Fire Brigades Union was due to take place this morning between 6am and 8am.
Graham Wilkinson, union representative for South Yorkshire FBU said: “We can only go by the support we get on the ground but it did feel successful.
It is only short periods we are going out for but we want to get the message across.
“The pensions don’t come in until 2015, so I’d be very surprised if there wasn’t more action in the near future.”
Just eight engines were covering South Yorkshire manned by officers with just three weeks of training, according to union bosses.
Mr Wilkinson said: “These contingency crews who cover strikes get three weeks’ training and can only do the basics.
“Normally there are 23 engines covering the area.”