The Fire Brigades Union said their planned strike is a "warning shot to government" over the ongoing pensions row.
Matt Wrack, Fire Brigades Union General Secretary, said:
This initial strike is a warning shot to government. Firefighters could not be more serious about protecting public safety and ensuring fair pensions.
Governments in Westminster and Cardiff have simply refused to see sense on these issues.
It is ludicrous to expect firefighters to fight fires and rescue families in their late-50s: the lives of the general public and firefighters themselves will be endangered.
None of us want a strike, but we cannot compromise on public and firefighter safety.
More top news
UK defence secretary says so-called Islamic State group will only be defeated by force.
Sheriff's deputies were called to the scene in LA County after residents reported hearing muffled crying.
Further one in eight expect to be aged between 71 and 80 years when they finally stop work, according to survey.