NIOSH-approved respirators cannot be altered to improve fit
"The National Institute for Occupational Safety and Health (NIOSH) identified concerning statements in the User Instructions for several filtering facepiece respirators (FFRs) manufactured by NIOSH approval holders. These statements instruct the user to modify the FFR in order to improve the fit. An example of the suggested modification includes tying knots in the headbands to create a tighter fit.
The instruction to “shorten them [the headbands] by knotting” directly conflicts with the NIOSH Caution and Limitation N – Never substitute, modify, add, or omit parts. Use only exact replacement parts in the configuration as specified by the manufacturer.
In some limited instances, NIOSH failed to identify this concern prior to issuing approvals. As a result, FFRs were distributed with User Instructions that included similar statements. As these issues are identified, NIOSH notifies the NIOSH approval holders to correct their User Instructions. This notice is intended to notify users in occupational settings that are required to use respiratory protection if users received the previous instructions and cannot achieve a proper fit, the respirator configuration should not be modified in any way. Another product should be selected for use.
In addition to filtering facepiece respirators, NIOSH reminds users that all NIOSH-approved respirators and their components should not be modified. Modifications will result in those respirators no longer meeting NIOSH approval requirements and may lead to a reduction or loss of expected protection for the user."
(Info provided from a CDC email update sent on 9/1/2022.)