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.