evidence: Carbon dioxide increases with face masks but remains below short-term NIOSH limits - PMID: 33858372 - PMCID: PMC8049746 - DOI: 10.1186/s12879-021-06056-0 Carbon dioxide increases with face masks but remains below short-term NIOSH limits [...] Conclusion: Although, significant increase in CO2 concentrations are noted with routinely used face-masks, the levels still remain within the NIOSH limits for short-term use. Therefore, there should not be a concern in their regular day-to-day use for healthcare providers. The clinical implications of elevated CO2 levels with long-term use of face masks needs further studies. Use of PAPR prevents relative hypercapnoea. However, whether PAPR should be advocated for healthcare workers requiring PPE for extended hours needs to evaluated in further studies.