Borehamwood firefighters have walked out in the first day of the Hertfordshire fire strikes.
Firefighters have taken their place to picket at Cheshunt, Broxbourne, as part of industrial action over pensions.
Tony Smith, secretary of Hertforshire Fire Brigade Union, said: "The Borehamwood staff have gone to support the strike at Cheshunt, where a member of staff has recently been sacked, so their emotions are running very high."
Speaking last week, Mr Smith said that the strikes were firefighters' only option: "The Government has failed to make any offer since the last strikes. We have been talking for months discussing all sorts of angles and ways and we have tried to negotiate. We are very disappointed about this."
Firefighters are due to strike until 5pm today; between 2pm and 2am on May 3 and on May 4 between 10am and 3pm.
There will also be a ban on voluntary overtime across England and Wales from 3pm on May 4 until noon on May 9.