How much do respirators protect healthcare workers from COVID19?

In the context of the current Covid-19 pandemic, it became clear that while performing treatment procedures on contaminated patients, medical personnel could be exposed to SARS-CoV-2 virus. Respirators (intended to protect the healthcare workers) provide a tight seal with the face of the wearer, and must meet rigorous standards on high filtration efficiencies and rigorous certification. In Europe, respirators such as FFP1, FFP2 and FFP3 are certificated by 'Conformité Européenne' (CE) in order to meet filtration efficiencies of 80%, 94% and 99% against particles of 0.3µm, respectively. Taki...