page_title: Respirator assigned protection factors
section_title: Terminology to describe the different PF, and methods for APF development
hierarchical_section_title: Respirator assigned protection factors / Background / Terminology to describe the different PF, and methods for APF development
caption_attribution_description: Русский: Показаны значения коэффициентов защиты (отношения концентрации вредных веществ снаружи лицевой части к концентрации под лицевой частью, во вдыхаемом воздухе) у фильтрующих респираторов с принудительной подачей воздуха (Powered Air-Purifying Respirator PAPR) под не плотно прилегающую лицевую часть (шлем или капюшон). Результаты измерений во время работы на рабочих местах выявили неожиданно низкую эффективность СИЗОД: вместо снижения загрязнённости воздуха в 1000 раз и более (что они стабильно показывали в лабораторных условиях), коэффициенты защиты (Protection Factors PF) снижались до 23-24, и как правило не превышали 200. Полученные результаты заставили изменить область допустимого применения таких СИЗОД - с 1000 ПДК до 25 ПДК (США) и до 40 ПДК (Великобритания) English: The diagram show 92 values ​​of the Workplace Protection Factors WPFs (the ratio of the concentration of harmful substances in the breathing zone outside the facepiece to the in-facepiece concentration, in the inhaled air) of Powered Air-Purifying Respirators (PAPRs) with loose-fitting facepieces (hood or helmet). These workplace (field) studies revealed unexpectedly low RPD performance: instead of reducing air pollution in 1000 times and more (that they consistently demonstrated in the laboratory conditions), the worcplace PF decreased up to 23-24, and usually does not exceed 200. These results led to change the Assigned Protaction Factors (allowable area of ​​usage) of such PPE - from 1000 PEL to 25 PEL (in US); and up to 40 OEL (in UK)
context_page_description: The respiratory protective devices can protect workers only if their protective properties are adequate to the conditions in the workplace. Therefore, specialists have developed criteria for the selection of proper, adequate respirators, including the Assigned Protection Factors - the decrease of the concentration of harmful substances in the inhaled air, which to be provided with timely and proper use of a certified respirator of certain types by taught and trained workers, when the employer performs an effective respiratory protective device programme.
context_section_description: The experts used the results of measurements at the laboratories and at the workplaces to develop more completely terminology for description of the respirators' performance; and this terminology has been applied officially, and in the preparation of research results for publication. Specialists began to use different terms to describe the protection factors, which were measured at workplaces with continuous use of respirators; and measured in the workplace when the workers used of respirators intermittently; measured not in the workplace while fit testing; measured in the laboratories under the simulation workplace's conditions; and for the protection factors, that can be expected (in most cases) when the workers properly used the respirators at the workplace.
  A significant difference between respirator performance in the laboratories compared to the efficiency at the workplaces not allowed to use the laboratory results to predict the degree of protection offered in practice. And instability of respirators' protective properties (for the same RPD design, and in the same usage conditions) prevented evaluate their efficiency. For solving these problems, scientists Donald Campbell and Steven Lenhart suggested to use the results of measurements of Workplace PF values for development of Assigned (expected in practice) PF values (APF) - as the lower 95% confidence interval of WPF values. The results of measurements of WPF has been used in the development of APF by ANSI (for the recommended standard, that is not mandatory). The same was made during the development of the APF by OSHA (in the development of the standard, that is mandatory for the employer).
caption: The diagram show 92 values of the Workplace PFs of PAPRs with loose-fitting facepieces (hood or helmet). After them, the Assigned Protection Factors of such PAPRs were reduced from 1000 to 25 (US) and to 40 (UK)
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