3M and Amazon have sold out of Powered Air Respirators, much less any other respirators or masks. My grandparents could find and buy only non-powered Respirators like 3M's FF-402:
Here are the drawbacks of N95, N99, N100, R95, P95, or P100 respirators:
CONCLUSIONS:
Healthcare providers may develop headaches following the use of the N95 face-mask. Shorter duration of face-mask wear may reduce the frequency and severity of these headaches.
What are the effects of wearing a N95 mask?
This may be due to the mask causing increased resistance to breathing, and a reduction in the volume of air breathed. For most people this is not serious.
However, some elderly people, people with lung or heart conditions, and women in the later stages of pregnancy may already have reduced lung volumes or breathing issues.
You should take a break from using a N95 mask if you feel uncomfortable.
The Physiological Impact of N95 Masks on Medical Staff - Full Text View - ClinicalTrials.gov
Wearing N95 masks results in hypooxygenemia and hypercapnia which reduce working efficiency and the ability to make correct decision.
Medical staff are at increased risk of getting 'Severe acute respiratory syndrome'(SARS), and wearing N95 masks is highly recommended by experts worldwide. However, dizziness, headache, and short of breath are commonly experienced by the medical staff wearing N95 masks. The ability to make correct decision may be hampered, too. The purpose of the study was therefore to evaluate the physiological impact of N95 mask on medical staff.
Assume that you must wear a respirator for hours, and can't "take a break from using" them. If you feel this "hypooxygenemia and hypercapnia", then:
What can you do?
Can you stand in front of a fan to try to ventilate the expelled air inside the respirator?