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Seguridad

NOM-004-STPS

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).

What you need to know

  • 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.

Full definition

NOM-004-STPS-1999 is a critical Mexican Official Standard that outlines safety conditions for machinery and equipment in workplaces, aimed at protecting workers from a range of mechanical hazards inherent in industrial environments. Established by the Mexican Secretariat of Labor and Social Welfare (STPS), this standard mandates comprehensive risk assessments to identify mechanical hazards associated with machinery, such as entrapment, cutting, shearing, crushing, projecting, and impact. Employers are responsible for conducting thorough risk studies for each machine they operate, ensuring that all potential dangers are recognized and mitigated. This foundational step is crucial for developing effective safety plans and protocols within an organization.

One of the core requirements of NOM-004-STPS is the implementation of guards and safety devices on all hazardous moving parts of machinery. These protections can take various forms, including fixed guards that provide a permanent barrier, interlocked guards that halt machine operation when opened, adjustable guards that can be modified for different tasks, and presence-sensing devices that detect human presence and stop machines immediately. Each type of guard plays a vital role in minimizing risk and ensuring safe operation in dynamic industrial settings. Additionally, the standard mandates the use of lockout/tagout (LOTO) procedures, which are essential for ensuring that machines are properly shut down and unable to be started up again until maintenance and repair work is completed safely.

Furthermore, safety devices such as emergency stop buttons, limit switches, interlocks, and two-hand controls are stipulated to enhance the safety of machine operations. The emergency stop, often characterized by a red mushroom button on a yellow background, is particularly important, as it provides a quick means for operators to halt machinery in case of an emergency. Regular preventive maintenance is also required to ensure that all safety devices and guards remain functional and effective. Training is a crucial component of compliance, as NOM-004-STPS mandates that all workers receive education on machine hazards and safe operating procedures. Additionally, the standard specifies color coding for safety signs and equipment per NOM-026-STPS, further reinforcing the importance of visual safety cues in the workplace. Enforcement of NOM-004-STPS is rigorous, with STPS inspectors authorized to conduct workplace inspections and impose fines for non-compliance, underscoring the critical importance of adherence to these safety regulations for the well-being of workers across Mexico's industrial sectors.

What you need to know

  • What you need to know: NOM-004-STPS-1999 targets mechanical hazards in workplaces, requiring a thorough risk assessment for each machine.
  • Guards must be installed on all hazardous moving parts, including fixed, adjustable, and presence-sensing types.
  • Lockout/tagout (LOTO) procedures are required for safe maintenance of machines, preventing accidental startups.
  • Safety devices like emergency stop buttons and limit switches must be functional and regularly maintained.
  • Training on machine hazards and safety procedures is mandatory for all workers under this standard.

Industrial applications

  • 1Manufacturing plants implementing machinery safety standards to minimize injury risk.
  • 2Workshops conducting routine maintenance on machines using LOTO procedures.
  • 3Assembly lines using fixed and adjustable guards to protect workers from moving parts.
  • 4Heavy machinery operations where emergency stop devices are crucial for worker safety.
  • 5Training sessions where workers are educated on machine hazards and safe operation practices.

Common mistakes

  • ✕Failing to conduct comprehensive risk assessments for all machinery, leading to unrecognized hazards.
  • ✕Neglecting the maintenance of safety devices, resulting in ineffective protection measures.
  • ✕Inadequate training for workers on the specific hazards associated with machinery they operate.
  • ✕Improper implementation of lockout/tagout procedures, increasing the risk of accidental machine start-up.
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Pro tip

Regular audits of safety devices and training programs can significantly reduce workplace accidents and ensure compliance with NOM-004-STPS.

Technical standards

  • NOM-004-STPS-1999: Safety conditions for machinery and equipment in workplaces.
  • OSHA 29 CFR 1910.212: Standards for machine guarding in the U.S.
  • EN ISO 12100: European standard for machinery safety.

Suppliers of safety products in Mexico

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Applicable standards

NOM-004-STPS-1999NOM-026-STPSNOM-004ISO 12100
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