Unions say they have the power to bring the NHS in the Westcountry to a standstill when they stage a four hour strike next month.
UNISON say their first walk out over pay in 32 years will also highlight deep concerns members have about cuts to the service.
Hospitals in the Westcountry said they have contingency plans in place to deal with the mass four hour walk-out.
Helen Eccles, UNISON South West Head of Health, said the Government should not underestimate the strength of feeling.
"NHS members don't take action often or lightly," she said.
"For many of our members this will be the first time they walk out as the last action over pay was 32 years ago. The NHS runs on the goodwill of its workers, but this Government has shown utter contempt for them.
"Tens of thousands of UNISON members across the South West have told us they will undertake industrial action because they haven't had a pay rise in four years, the gap between pay and bills is getting bigger and they are really struggling to make ends meet.
"The fact that the government has decided that a 1% pay rise for NHS workers isn't affordable when at the same time an 11% award is made to MPs seems to show that the work of NHS staff is neither recognised or valued. NHS staff simply can't afford for this to continue; a motivated and valued workforce is essential in delivering high quality services to patients."
Ms Eccles said they were working with NHS employers to minimise the impact on patients, but added it was not too late for health secretary Jeremy Hunt to act.
The stoppage will be between 7am and 11am on Monday October 13, which will be followed by four days of action short of strike action between October 14 and 17 when members will stop working through their breaks and instead take the time to which they are entitled.
A strong 68% voted yes for industrial action and 88% to action short of strike action in a ballot which closed on September 18.
Earlier this year, the government decided to ignore the NHS Pay Review Body's recommendations and instead give a 1% non-consolidated increase only to staff at the top of their incremental scale. Because the award is non-consolidated it will not count towards pension entitlements or shift pay and will be wiped away at the end of March 2016, meaning wages will go back to their April 2013 level.
A total of 10 unions are balloting in the NHS over pay and UNISON action will be co-ordinated with them.
Health workers across the Westcountry said they were being forced into the action.
Jim Clawson, who works at Devon Partnership Trust, said: "I've voted yes as the recent decision to ignore the Pay Review Body recommendation showed a total disregard for NHS staff and their patients."
Trudie Brailey, who works at Northern Devon Healthcare NHS Trust, said: ""This result shows how very upset and angry a our members feel, they truly have had enough of this selfish government who undervalues the valuable services that they provide."
Kevin Marsh, director of nursing at Northern Devon Healthcare Trust, said plans were in place to deal with the walk-out.
"We are in continual dialogue with trade unions over the planned industrial action on the morning of Monday 13 October.
"The trust will be fully prepared and we are experienced in ensuring our services continue during industrial action.
"Our priority is to ensure the impact on patients is kept to an absolute minimum. We will work closely with the staff involved in advance to ensure this happens.
"Patients who need emergency or urgent care are always prioritised.
"If any appointments or non-urgent operations have to be postponed, those patients affected will be notified in advance and we will do our best to ensure they are seen as soon as possible.
"Any decision to postpone will be based on which appointments could be rearranged most safely."
Tracey Cottam, director of transformation and organisational development at Royal Devon and Exeter Hospital, said they were prepared.
"We are aware of the intention of Unison to carry out industrial action during October.
"We have been actively anticipating the impact this action could have on have on our services. Whilst we have not yet received official notification from the Unions of strike action, we are engaging with our staff side colleagues to ensure continuity of care for patients.
"We are putting in place continuity plans to ensure that we can continue to provide seamless and high quality services in the event of industrial action taking place."
