Welsh firefighters join first of series of strikes in pensions row
Mid and West Wales Fire and Rescue Service is asking people to be cautious during the latest strikes.
Fire Brigades Union (FBU) members across Wales and England are walking out twice on Monday.
Firefighters are striking from 06:00 to 08:00 and 17:00 to 19:00 BST as part of action over the next eight days.
Assistant chief fire officer Rob Quin said: "It's really important that people do not become complacent and that they stay alert to the risks."
FBU members are carrying out a series of strikes over an eight-day period, prompted by a row over pensions and retirement benefits.
It is expected that union members across Wales will support the action.
Mr Quin added: "This latest notification from the FBU of forthcoming strike action is the most comprehensive we have seen since the dispute over pension reform between the government and FBU began in September last year.
"We have a wide range of safety advice available on our website and I would encourage everyone to find some time to familiarise themselves with it over this period."
The fire service said that, while it will still be responding to 999 call-outs with non-FBU affiliated staff, there is the chance of a reduced emergency response during the industrial action.
The two other fire services in Wales, North Wales and South Wales, are also putting in place contingency plans for the strike action.