Respirator assigned protection factors

Therefore, specialists have developed criteria for the selection of proper, adequate respirators, including the Assigned Protection Factors (APF) - the decrease of the concentration of harmful substances in the inhaled air, which (is expected) to be provided with timely and proper use of a certified respirator of certain types (design) by taught and trained workers (after individual selection with a tight-fitting mask and fit testing), when the employer performs an effective respiratory protective device programme.

However, the sole reliance on personal protective equipment for personnel is considered the least effective means of controlling hazards, for reasons including: non-usage of the respirators in the contaminated atmosphere; leakage of unfiltered air through the gaps between the mask and face; and delayed replacement of gas cartridges.

[10] Experts believed that the measurement of protection factors in the laboratory allows them to correctly evaluate, predict the RPD efficiency in the workplace conditions.

But after the detection of cases of excessive harmful exposure on employees who used high quality respirators with HEPA particle filters in the nuclear industry of the US, the experts changed their opinion.

[12] Dozens of such field studies have shown that the performance of serviceable respiratory protective equipment at the workplaces may be significantly less than in laboratory conditions.

Therefore, the usage of laboratory results to assess the real efficiency is incorrect; and can lead to a wrong choice of such respirators that can not reliably protect workers.

And instability of respirators' protective properties (for the same RPD design, and in the same usage conditions) prevented evaluate their efficiency.

Finally, in the absence of this information, specialists could use the results of Simulated WPF measurements; or estimates of competent experts.

Additional studies,[24] from 1986 and 1981, agreed with the result from the Myers et al. 1986 study: the minimum values of the workplace protection factors of two models of respirators were 31 and 23; and leakage of unfiltered air attained 16% in some cases in wind tunnel at 2 m/s air velocity[25] Therefore, the use of such RPD types was limited 25 PEL in the United States,[22] and 40 OEL in the UK.

However, scientific studies have shown that although such test increases the effectiveness of protection, the risk of leakage of large amounts of unfiltered air is maintained.

So, specialists recommend not allowed usage negative pressure half mask respirators then harmful substances' concentrations exceeds 10 PEL.

The fact that the employee is in a non-polluted atmosphere some part of working time provide additional protection of his health, and therefore, the requirements to the efficiency of the respirator may be less stringent.

The development of the Assigned PF in the United States and Britain were based on measurements of the effectiveness of respirators in the workplace (after statistical processing).

Most European countries (except UK) did not conduct very complex and expensive studies on the effectiveness of respirators in the workplaces, or spent very little of such research.

Therefore, it may be that some countries do not take full account of results of foreign researches (that showed a significant difference between the effectiveness of respirators in a laboratory environment; and in applying them in the workplaces).

The minimum values of the workplace protection factors (WPF) of each of the three negative pressure full face mask models were 11, 17 and 26.

State standard in India[38] points to the need to use the workplace protection factors for restricting the permissible use of respirators, but does not set any values of the APFs.

[39] This document only listed the values of APFs in several European countries (for reference); and declares the inadmissibility of the use of laboratory efficiency for predicting the protective properties at the workplace.

This contributes to errors, and the usage of such respirator's types, which are not able to reliably protect the workers due to its design (even at high quality of specific certified models).

3 - There is no information that would show that the values of these APFs were developed so that the difference in efficiency at the workplaces and in the laboratories is taken into account to the full extent (as in the US and UK).

The results of such measurements are used to assess whether short-term inhalation of harmful substances may lead to irreversible and significant deterioration of health, or death (IDLH concentrations).

If concentrations exceed the IDLH, the standard allows the use of only the most reliable respirators - SAR or self-contained breathing apparatus: with pressure-demand air supply in the full facepiece mask ( §(d)(2)[22]).