If you are not yet infected or have to be in contact with people having some symptoms there is no point using a mask unless it's class FFP3 or better because the virus also spreads as an aerosol. If you have a mask save it for anyone having symptoms to protect other people.

https://www.nejm.org/doi/10.1056/NEJMc2004973

https://www.who.int/emergencies/dise...w-to-use-masks

When ever possible washing hands with soap is better than using hand disinfectant.