There were two 999 calls during the firefighters strike this morning when crews walked out between 6.30am and 8.30am.
The calls were to a false alarm in Cheshunt and an automatic fire alarm in Potters Bar, which also turned out to be a false alarm.
Firefighters represented by the Fire Brigades Union are locked in a row with the government over working longer and receiving less in pension payouts when retirement arrives.
During the industrial action shifts are covered by non-striking firefighters and also some who have recently retired but have agreed to return to stations to fill the void.
The striking action has previously been criticised by Hemel Hempstead MP Mike Penning, who is a former firefighter himself.
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