A system for completing fit testing on a mask comprising: a mask ; an electronics module mounted on the interior of the mask , wherein the electronics module comprises one or more sensors configured to detect the pressure of the interior of the mask, and wherein the electronics module is configured to: detect the pressure of the interior of the mask during a negative fit test, wherein all inlet(s) to the mask are covered by the user, and the user inhales and holds their breath for approximately 10 seconds; indicate that the negative fit test has passed when the pressure of the interior of the mask is below a negative pressure threshold; detect the pressure of the interior of the mask during a positive fit test, wherein all outlet(s) to the mask are covered by the user, and the user exhales and holds their breath for approximately 10 seconds; indicate that the positive fit test has passed when the pressure of the interior of the mask is above a positive pressure threshold; characterised in that when the fit tests are passed, the electronics module enters into an end of service life indicator (ESLI) mode; wherein the electronics module is further configured to detect the pressure within the mask; and indicate end of service life when the pressure exceeds an ESLI threshold. a mask ; an electronics module mounted on the interior of the mask , wherein the electronics module comprises one or more sensors configured to detect the pressure of the interior of the mask, and wherein the electronics module is configured to: detect the pressure of the interior of the mask during a negative fit test, wherein all inlet(s) to the mask are covered by the user, and the user inhales and holds their breath for approximately 10 seconds; indicate that the negative fit test has passed when the pressure of the interior of the mask is below a negative pressure threshold; detect the pressure of the interior of the mask during a positive fit test, wherein all outlet(s) to the mask are covered by the user, and the user exhales and holds their breath for approximately 10 seconds; indicate that the positive fit test has passed when the pressure of the interior of the mask is above a positive pressure threshold; characterised in that when the fit tests are passed, the electronics module enters into an end of service life indicator (ESLI) mode; wherein the electronics module is further configured to detect the pressure within the mask; and indicate end of service life when the pressure exceeds an ESLI threshold. detect the pressure of the interior of the mask during a negative fit test, wherein all inlet(s) to the mask are covered by the user, and the user inhales and holds their breath for approximately 10 seconds; indicate that the negative fit test has passed when the pressure of the interior of the mask is below a negative pressure threshold; detect the pressure of the interior of the mask during a positive fit test, wherein all outlet(s) to the mask are covered by the user, and the user exhales and holds their breath for approximately 10 seconds; indicate that the positive fit test has passed when the pressure of the interior of the mask is above a positive pressure threshold; characterised in that when the fit tests are passed, the electronics module enters into an end of service life indicator (ESLI) mode; wherein the electronics module is further configured to detect the pressure within the mask; and indicate end of service life when the pressure exceeds an ESLI threshold. <EOS>