Particle – small discrete mass of solid or liquid matter (PNISO 4225:1999)

Smoke – emitted aerosol, usually resulting from combustion (PNISO 4225:1999)

Filtration – removal of particles from liquid or gas (PNEN 12792:2006)

Inhalable fraction – aerosol fraction inhaled through the nose and mouth, posing a health risk after deposition in the airways

Respirable fraction – aerosol fraction penetrating the airways, posing a health risk after deposition in the gas exchange region

Particle number concentration – number of dispersed-phase particles in the aerosol per unit of gas volume (PNISO 4225/Ak:1999)

Particle number fraction – ratio of number of particles in a specific size range to the overall number of dispersed or settled particles (PNISO 4225/Ak:1999)

Particle mass fraction – ratio of mass of particles in a specific size range to the overall mass of dispersed or settled particles (PNISO 4225/Ak:1999)

Mist – loose term referring to a suspension of droplets in gas

Threshold Limit Valve – Time Weighted Average (TLV-TWA) – weighted average concentration to which a worker can be exposed during an 8-hour daily and average weekly working time specified in the Labour Code for a working lifetime without adverse effects to the worker's health and to the health of the worker's future generations (Regulation of the Minister of Labour and Social Policy of 29 November 2002, Journal of Laws of 2002, No. 217, item 1833)

Threshold Limit Value – Short-Time Exposure Limit (TLV-STEL) – average concentration which should not adversely affect the worker's health if it occurs in the work environment for up to 15 minutes and with a frequency of up to 2 times per working shift, at intervals of at least 1 hour (Regulation of the Minister of Labour and Social Policy of 29 November 2002, Journal of Laws of 2002, No. 217, item 1833)

Threshold Limit Value – Ceiling Limit (TLV-CL) – concentration which must not be exceeded at any time in the workplace due to a health or safety hazard (Regulation of the Minister of Labour and Social Policy of 29 November 2002, Journal of Laws of 2002, No. 217, item 1833)

Vapour – Gaseous phase of matter that can exist simultaneously in a liquid or solid state (PNISO 4225:1999)

Dust – general term applied to solid particles of different dimensions and origin generally remaining suspended in a gas for a certain time (PNISO 4225:1999)

Fine dust – small solid particles, conventionally taken as those particles below 75 μm in diameter, which settle out under their own weight but which may remain suspended for some time

Coarse dust – airborne solid particles in the atmosphere or flues (PNISO 4225:1999)

Respirable dust – collection of particles passing through a size-selective inlet with particle size rating described by a logarithmic normal probability function with an average aerodynamic diameter of 3.5 ± 0.3 µm and standard geometric deviation of 1.5 ± 0.1 (Journal of Laws of 2002, No. 217, item 1833)

Smog – (term derived from the terms smoke and fog): Extensive atmospheric pollution by aerosols, arising partly through natural processes and partly from human activities (PNISO 4225:1999)

Personal protective equipment for protection against chemical pollutants and dust – equipment worn or held by the worker for protection against harmful chemical pollutants and dust in the work environment, including any accessories and fittings designed for this purpose (Regulation of the Minister of Labour and Social Policy of 26 September 1997 on the general occupational health and safety regulations – Journal of Laws of 2003, No. 169, item 1650, amended by Journal of Laws of 2007, No. 49, item 330)

Limit (hygienic normative) – statutory average concentration of a harmful factor to which the results of the measurements of this factor in the air of the work environment are compared to determine the exposure of workers (PNISO 4225/Ak:1999)

Cut-off – Size of particles at which the retention efficiency of an instrument device drops below a specified value under defined conditions (PN-ISO 4225:1999)

Respirable fibres – fibres longer than 5 µm with a maximum diameter of less than 3 µm and length-to-diameter ratio greater than 3 (Journal of Laws of 2002, No. 217, item 1833)