Background
The area I live in has a regulation that people should wear PPE when visiting grocery stores, etc. There is a shortage of PPE. I have access to some non-reusable FFP2-class respirators that are intended to be used during a 8 hours shift (similar to this one). Reuse of disposable respirators has been suggested as a crisis measure during the shortage. I have been reusing my respirators for a while, but by now I have used each of them for more than 8 hours.
Until I can replenish my stock, I have a choice between using the repsirators beyond the designated 8 hours, or resort to cloth masks, which are widely available / widely used in my area. A cloth mask is basically nothing more than a piece of cloth that can be attached to one's face.
My research so far
I'm by no means an expert, so correct me if I'm wrong. From what I understand cloth masks offer almost no protection against viruses. Respirators, on the other hand, offer some degree of protection due to being able to filter out particles/droplets from the inhaled air thanks to the electrostatic charge of the filter material. However, I wasn't able to find any info on the following:
Question
What happens to the respirator during the prolonged use?
Why is the use time limited? Is it because the contamination of filter layers reduces the electrostatic charge?
Most importantly, can a respirator at some point become less useful / more harmful than a cloth mask? (assuming that the user knows how to don/doff and store the respirators properly).