PPE is used when engineering, work practice and administrative controls are not possible or do not provide suitable protection for workers.
Explanation:
PPE stands for Personal Protective Equipment. Examples are safety glasses, earplugs, masks and gloves.
OSHA (Occupational Health and Safety Administration) is the governmental agency in the USA that ensures a safe working environment.
OSHA enforces employers to protect their employees from working environment hazards that can't be controlled for. To do this, OSHA indicates the use of Personal Protective Equipment (PPE).