Hello LoveAO,

                     l assume you mean to use the air purifier to scrub the air inside the house and attempt to filter out any airborne virus,In order to do that you would need a very sealed house and an awful lot of purification power in order to put all the volume of air through the filter resulting in a constant cycle.Personally l think you are approaching  this the wrong way insomuch that dust particles remain suspended for up to 36 hours in a still environment,and that dust particles measured in small microns can play host to virus piggybacking upon them,and it is these that can be breathed into the farthest recesses of your lungs.A number of years ago  l ran trials for rentokil for industrial ionisers in the farming industry,which gave a picture of what was happening. A good airflow never allow these particles to remain suspended since they are carried along in the airflow.Good ventililation also points to a colder background as we approach winter,and a chemo patient will feel the cold.

                                                                       So the option is a very powerful purifier (s) that cover the house or accompany the patient to whatever room they occupy, possibly an ioniser to settle fine dust,or good ventilation ensuring the patient is kept warm if the room is not,layers of clothes spring to mind.Fresh oxygenated air would be better than stale for a patient under stress experiencing laboured breathing.

                                                                                                 l  had career in intensive livestock production,and the biggest killer was the stress bought on by inadequate ventilation,being the trigger for all manner of ills to seize their opportunity.Never saw pnuemonia bought on by a cold draughtfree environment,but witnessed far too much bought on by insufficient ventilation and warm humid air.The message that emerged  waqs that in insufficient ventilation you need to capture the dust from the environment,the better option was to increase airflow without creating draught

                                                                                                                     Food for thought and l hope your mum continues to make good progress,
                                                    David