Work according to the STOP strategy

Because working with hazardous substances entails risks, you take measures to limit exposure and the risk of an accident as much as possible. The following occupational hygiene strategy or STOP strategy applies in the specified order: 

1. Substitution. Replace the hazardous substance with a non-hazardous or less hazardous substance. If it is not possible to replace a hazardous substance or to prevent exposure to it, you strive for the minimum possible exposure to that substance (the ALARA principle: As Low As Reasonably Achievable). 
2. Technical measures. Work with the hazardous substance in a room with boosted room ventilation (laboratory), work with the substance in a fume hood, in a ventilated casing or use point extraction. 
3. Organizational measures. Limit the duration of exposure and the number of employees exposed. 
4. Personal protective equipment (PPE). Use personal protective equipment such as lab coats, gloves, safety goggles, or face masks.