Full definition
Mexican Official Standard NOM-004-STPS-1999 "Safety conditions for machinery and equipment in workplaces" — the primary Mexican regulatory standard for protecting workers from mechanical hazards posed by industrial machinery. Key requirements: (1) Risk study — employer must identify all mechanical hazards (entrapment, cutting, shearing, crushing, projecting, and impact) for every machine. (2) Guards and safety devices — machines must have guards on all hazardous moving parts (point of operation, power transmission, and auxiliary parts); types include fixed, interlocked, adjustable, and presence-sensing devices. (3) LOTO procedures — written lockout/tagout procedures required for all energy sources during maintenance and repair. (4) Safety devices — emergency stops (red mushroom button on yellow background), limit switches, interlocks, two-hand controls. (5) Maintenance — preventive maintenance program to keep guards and safety devices functional. (6) Training — all workers must be trained on machine hazards and safe operating procedures. (7) Color coding — safety colors and signage per NOM-026-STPS. Enforcement: Mexican labor authorities (STPS inspectors) conduct workplace inspections and can impose fines for non-compliance. NOM-004 is equivalent in scope to OSHA 29 CFR 1910.212 (US) and EN ISO 12100 (European machinery safety).