World Health Organization
It draws on interim advice produced by WHO and national agencies, and also expert opinion [9,11,12,15,29] General infection prevention and control measures People feeling ill with respiratory symptoms should be encouraged to contact healthcare services to seek medical advice by telephone or telemedicine/online.
If possible, a physical barrier such as glass or a plastic teller window can be used to avoid direct contact and keep the distance; in such case no PPE is necessary  If available, provide a surgical mask for patients with respiratory symptoms (e.g. cough) Healthcare workers performing aerosol-generating procedures (AGP), such as swabbing , should wear the suggested PPE set for droplet, contact and airborne transmission (gloves, goggles, gown and FFP2/FFP3 respirator)  If there is a shortage of FFP2/FFP3 respirators, healthcare workers performing procedures in direct contact with a suspected or confirmed case (but not at risk for generating aerosol) can consider
While swabbing patients, healthcare personnel can use the same respirator for several patients for a maximum of 4 hours without having to remove the respirator, as long as it is not damaged or soiled, unless the manufacturer explicitly advises against this .
If there is no physical separation between the front and the back of the ambulance, a surgical mask should be considered .
The use of the same respirator while treating multiple patients should be considered; the maximum time a respirator can be worn is 4 hours, as long as it is not removed between patients or contraindicated by the manufacturer .
If visitors keep at least 1 meter away from a patient for the duration of the visit, and PPE availability is limited, only a surgical mask may be worn .
In addition, the use of heavy-duty gloves and boots should be considered .
Coordinated supply chains for PPE should ensure distribution of such materials to healthcare systems in order to reduce the potential for healthcare-associated transmission to vulnerable groups and healthcare workers .
The main priorities in this document for rational use are in concordance with detailed guidance published by WHO in February 2020 .
Respirators can be used for up to 4 hours for multiple patients without removing them , unless the respirator is damaged, soiled or contaminated, for example a symptomatic suspected case coughing on them.
If there is an insufficient stock of respirators, then staff engaged in environmental cleaning and waste management should wear a surgical mask, in addition to gloves, goggles and gown .
15. World Health Organisation (WHO). Rational use of personal protective equipment for coronavirus disease 2019 (COVID-19) 2020 [updated 27 February 2020; cited 2020 8 March]. Available from: https://apps.who.int/iris/bitstream/handle/10665/331215/WHO-2019-nCov-IPCPPE_use-2020.1-eng.pdf.