The action by the FBU follows a week without talks between the union and county council fire chiefs, who are trying to reach an agreement over fire cuts in Hertfordshire - including the controversial cuts to Bovingdon fire station.
'We've been as flexible as we can be in dealing with the FBU's demands but they haven't moved an inch.'
Chief fire officer Roy Wilsher said fire cover across the county on strike days would be reduced from 43 engines to seven between 2pm and 10pm.
FBU secretary Andy McLean rejected claims that the union was unwilling to negotiate.
'We're ready to talk at any time, any place, anywhere.'
Mr McLean also rejected Mr Lloyd's claim that the FBU strikes were putting lives at risk.
He said: 'It's a little bit dangerous for people to claim that when they're proposing to close stations.'
The further strike dates are on Friday and Wednesday 26 and 31 May.