What are hazardous atmospheres characterized by?

Hazardous atmospheres are characterized by the presence of explosive, flammable, or toxic materials, which pose significant health and safety risks to individuals working in those environments. This includes situations where gases, vapors, or particulates can lead to combustion or toxic exposure. Understanding these hazards is crucial for implementing appropriate safety measures, such as ventilation, personal protective equipment, and monitoring systems to detect dangerous conditions.

The other options do not align with the definition of hazardous atmospheres. The absence of air contamination would suggest a safe environment, while dust particles alone do not constitute a complete definition of hazardous conditions. Additionally, normal atmospheric conditions would imply a lack of any dangerous elements, further distancing the context from what is considered a hazardous atmosphere. Recognizing the criteria that make an atmosphere hazardous is vital for ensuring the safety and health of workers in potentially dangerous settings.