Ambulance staff are being put at risk by a lack of protective equipment to guard them against coronavirus, according to a trade union.
GMB says its members are "scared" about their own safety and their families.
The union claims one in five ambulance staff in London are off sick with coronavirus-related sickness.
The government says hundreds of millions of protective items have been delivered to NHS staff around the country.
According to the GMB Union, 679 frontline ambulance crew in the London Ambulance Service are off sick due to Covid-19-related sickness.
Among those at work, some say they feel unprotected either because of a lack of or inadequate personal protective equipment (PPE).
Paul Turner is a union representative who has returned to front-line paramedic duties in the north west of England.
"We are crying out for better personal protective equipment. I am seeing some of the strongest characters in the ambulance service at the moment at breaking point," he says.
"Our aprons are disposable and flimsy and our sleeve protectors do not cover all of our jackets. We go from one patient to the next and our uniform is potentially contaminated. We also don't want to be taking Covid-19 home to our families.
"This PPE might be suitable in a controlled setting, but unfortunately in the ambulance world our settings are not controlled."
Public Health England advises that any clinician working within two metres of a suspected or confirmed Covid-19 patient should wear an apron, gloves, surgical mask and eye protection, depending on risk.
The BBC has received written statements from some paramedics who did not want to be identified.
One worker said: "Every day more of our colleagues are being struck down with high temperatures and other symptoms. I feel it's just a matter of time before it's my turn and then I could potentially take it home to my family.
"But if I was to be sent home the guilt would set in - my colleagues are out there dealing with this crisis unprotected and I wouldn't be with them."
Another said: "We take patients to hospital in flimsy paper masks, a plastic thin apron that flaps up in the slightest breeze and gloves. To see the level of PPE that hospital staff are wearing, compared to ours, is really frightening."
NHS workers are being tested if they or their families have coronavirus symptoms, but there are concerns it is not happening quickly enough.
A Department of Health and Social Care spokesperson said it was working closely with industry, social care providers, the NHS, NHS Supply Chain and the army to give the NHS and the wider social care sector protective equipment.
Every hospital, community pharmacy and ambulance trust has now had a PPE delivery, the spokesperson added.
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