The emergency shut-off switch on our machine is broken. Can workers still use it if we post a sign warning that the switch is non-functional?
No. You must take the machine out of operation until the switch is fixed.
A warning sign isn’t an adequate replacement for a required safety device. For one thing, workers may not see, understand or obey the sign. And even if they do, the “Lifeguard Not On Duty: Swim At Your Own Risk” is NOT an acceptable approach for managing hazards, especially machine hazards.
Bottom Line: Your duty under OHS laws isn’t just to notify workers of machine hazards but to use engineering controls to manage them. That includes ensuring all safety devices are in good working order before allowing workers to use a machine.