Hazardous area classification divides facilities into zones based on the probability and duration of explosive atmospheres, determining equipment requirements. This classification is essential for proper equipment selection and installation.
Zone 0 represents continuous explosive atmosphere (> 1000 hours/year) and requires the highest level of protection, though it is rare in practice. Zone 1 represents likely explosive atmosphere (10-1000 hours/year) and requires high level of protection, common in process areas. Zone 2 represents unlikely explosive atmosphere (< 10 hours/year) and standard protection is sufficient, making it the most common classification.
Classification factors include gas release frequency, ventilation effectiveness, gas dispersion characteristics, process conditions, and historical data. Understanding these factors helps determine the appropriate zone classification for each area.
Equipment requirements vary by zone: Zone 0 requires intrinsically safe or explosion-proof equipment, Zone 1 requires explosion-proof or increased safety equipment, and Zone 2 often allows standard equipment. Equipment must match gas group and temperature class for the specific application.
Standards include IEC 60079 series, NFPA 70 (NEC), ATEX directives, and local regulations. Proper classification determines equipment selection, affects installation costs, ensures safety compliance, and guides detector placement for optimal coverage.