The Professional Firefighters Union believes there's a staffing crisis in the sector

They start strike action today, calling for better pay and staffing levels.

Strike action's largely behind the scenes and won't affect those responding to fires and other emergencies.

Union National Secretary Wattie Watson says volunteers and their employers are being too heavily relied on.

She says Fire and Emergency NZ hasn't increased the number of firefighters since the 1990s and don't currently employ enough to cover that level of staffing.