To be clear, the following quote in the linked to post by tentseller is what we assumed MrLapLap would need help being protected against.

Dr. Yuen Kwok Yung:
“6. Health Authority announced that this virus is very serious. However, as the virus is found to be able to enter your body if your throat or throat mucous is dry, the one precaution they suggest which can be taken is to ensure your throat or throat mucous is always in a moist condition. In fact, they suggest not to allow your throat to become dry, as in 10 minutes of being dry, the virus will find ways to enter into your body. So do not refrain from drinking water, always have a bottle handy.
For adults, they suggest drinking 50-80cc of warm water; for children 30-50cc. Just drink if you feel your throat is dry. Do not hesitate. However drinking more than the amount recommended is not necessary, as it will just want to pass through your system. The idea is to “Keep your Throat Constantly Moist”

https://www.flyertalk.com/forum/31977011-post23.html

As mentioned, MrLapLap will certainly be falling asleep on these Cathay Dragon flights and, particularly on planes, this will guarantee his mouth and throat drying up. Having a mask should hopefully keep things a bit moister in there.

Same doctor also advises:
”7. Before end of March, try not to enter crowded places, MTR or public Transport, and wear a mask if necessary. ”

Was easier to comply in London than in Dhaka. Thanks again for helping me understand the US N95/N99 standards in relation to the UK’s FFP2/FFP3.

Should anyone else want a bit more data, there are tables here for the 3M Aura masks and what 3M recommend them for:
https://multimedia.3m.com/mws/media/1313154O/aura.pdf