Glossary of NR-33

Accredited calibration: Calibration performed by a laboratory accredited by the National Institute of Metrology, Quality and Technology – Inmetro.

Adjustment: An operation aimed at ensuring that a measuring instrument performs according to its intended use. The adjustment aims to update the reference point of the sensors.

Attendant: A worker designated to remain outside the confined space, responsible for monitoring, communication, and issuing evacuation orders to the workers inside.

Auto-zero (or clean air adjustment): A feature of gas detectors to establish a zero reference for all sensors monitoring flammable gases, vapors, and contaminants, as well as to adjust the oxygen sensor to the normal concentration of this substance in the air. This should be performed in a clean air environment by holding the equipment’s power button for a certain period to clear the readings and relieve any existing pressure in the equipment.

Authorized worker: A worker trained to enter the confined space, aware of their rights and duties, and knowledgeable about existing risks and control measures.

Bump test: A test intended to verify the functionality of sensors and alarms without measuring the sensors’ accuracy or making any necessary adjustments.

Calibration: An operation that establishes, under specified conditions, in a first step, a relationship between the values and measurement uncertainties provided by standards and the corresponding indications with associated uncertainties; in a second step, uses this information to obtain a measurement result from an indication.

Classified area: An area that is potentially explosive or likely to become explosive due to the presence of a mixture of air with flammable materials in the form of gas, vapor, mist, dust, or fibers, requiring special precautions for the installation, maintenance, inspection, and use of equipment, instruments, and accessories used in electrical installations.

Contaminants: Gases, vapors, mists, fumes, and dusts present in the atmosphere of the confined space.

Degree of protection: Numerical classification, preceded by the IP index, referring to the protection provided by an enclosure against access to hazardous parts, penetration of foreign solid objects, and/or penetration of water, verified through standardized testing methods.

Drowning: Inhalation of a non-bodily solid or liquid by submersion or immersion of the worker.

Electromagnetic radio frequency interferences: Receipt of unwanted information that disrupts the functioning of equipment used for atmospheric evaluations, potentially causing reading errors.

Emergency and rescue team: Workers trained and equipped to rescue and provide first aid to workers in an emergency.

Engulfment: Envelopment and capture of a person by particulate solid material capable of causing unconsciousness or death.

Entry Permit: A document containing a set of control measures for safe entry and work, as well as emergency and rescue measures in confined spaces.

Entry supervisor: A person trained to operate the entry permit, responsible for completing and signing the PET for safe entry and work within confined spaces.

Hazardous energy: Any form of energy that can cause death, injury, or health damage to workers.

IDLH Atmosphere – Immediately Dangerous to Life or Health: Any atmosphere that presents an immediate risk to life or produces an immediate debilitating effect on health.

Inerting: Displacement of the existing atmosphere in a confined space by an inert gas, resulting in a non-combustible atmosphere with an oxygen deficiency.

Initial atmosphere evaluations: A set of preliminary measurements conducted in the atmosphere of the confined space.

Intrinsically safe: A condition where the equipment cannot release sufficient electrical or thermal energy to ignite a given explosive atmosphere, under normal or abnormal conditions, as stated in the equipment’s certificate of conformity.

Lockout: A device that prevents the release of hazardous energies, such as pressure, steam, fluids, fuels, water, and others, aiming to contain dangerous energies for safe work in confined spaces.

Open flame: A mixture of incandescent gases emitting energy, also called a flame or fire.

Oxygen deficiency: An atmosphere containing less than 20.9% oxygen by volume at normal atmospheric pressure unless the reduction in percentage is duly monitored and controlled.

Oxygen enrichment: An atmosphere containing more than 23% oxygen by volume.

Rescue plan: A pre-written document used by the team executing the rescue, containing the rescue and first aid planning.

Proficiency: Competence, aptitude, training, and skill combined with experience.

Pure oxygen: An atmosphere containing only oxygen (100%).

Purging: A cleaning method that makes the interior atmosphere of the confined space free of gases, vapors, and other unwanted impurities through ventilation or washing with water or steam.

Responsible technician: A legally qualified or skilled professional in occupational safety, authorized to implement the measures provided in item 33.3.2 of this NR.

Spark: A glowing particle generated in mechanical processes such as grinding, polishing, cutting, or welding.

Tagging: Placing a label on an energy isolating device to indicate that the device and the equipment being controlled cannot be used until the label is removed.

Response test or “bump test”: Has the purpose of verifying the functionality of sensors and alarms without measuring the accuracy of the sensors or making any necessary adjustments.