What is Assigned Protection factor in respiratory equipment? How many types of APF from different respiratory equipment? What is maximum use concentration (MUC’s)?

What is Assigned Protection factor in respiratory equipment? How many types of APF from different respiratory equipment? What is maximum use concentration (MUC’s)?

< APF helps in selection of right respiratory equipment at workplace. We need two things permissible exposure limit and workplace concentration. Divide workplace concentration by exposure limit, result will decide the required minimum APF.

Example:

Exposure limit

Permissible Exposure Limit (PEL) for asbestos is 0.1 fiber per cubic centimeter of air as an eight-hour time-weighted average (TWA), with an excursion limit (EL) of 1.0 asbestos fibers per cubic centimeter over a 30-minute period. The employer must ensure that no one is exposed above these limits.

Workplace concentration

Asbestos is 0.5 fiber per cubic centimeter of air as an eight-hour time-weighted average (TWA)

Assigned Protection Factor of Respiratory =    0.2/0.1

                                                                             = 5

So, in this case respiratory having assigned protection factor minimum to 5 can be used.

Maximum Use Concentration = APF X PEL= 5 X 0.1= 0.5

So here if we are using APF rating 5 then 0.5 fiber per cubic centimeter will be the maximum atmospheric concentration of a hazardous substance from which an employee can be expected to be protected when wearing a respirator.

NOTE:

a-      Whenever the exposures approach the MUC, then the employer should select the next higher class of respirators for the employees.

b-      Employers must not apply MUCs to conditions that are immediately dangerous to life or health (IDLH); instead, they must use respirators listed for IDLH in the standards.

c-       When the calculated MUC exceeds the IDLH level for a hazardous substance, or the performance limits of the cartridge or canister, then employers must set the maximum MUC at that lower limit.

d-      Respirator selection should be done based on the state of workplace agent physical form.

Type of Respirator and their APF

a-      Half mask/ Dust mask= APF is 10

b-      Half mask (Cartridge based Elastomeric)= APF is 10

c-       Full Face piece= APF is 50

d-      Powered Air-Purifying Respirator (PAPR)= APF is 25

e-      Full Face piece SCABA = APF is 10,000

Definitions:

Assigned Protection Factor (APF) means the workplace level of respiratory protection that a respirator or class of respirators is expected to provide to employees when the employer implements a continuing, effective respiratory protection program.

Maximum Use Concentration (MUC) means the maximum atmospheric concentration of a hazardous substance from which an employee can be expected to be protected when wearing a respirator, and is determined by the assigned protection factor of the respirator or class of respirators and the exposure limit of the hazardous substance. The MUC usually can be determined mathematically by multiplying the assigned protection factor specified for a respirator by the permissible exposure limit (PEL), short-term exposure limit, ceiling limit, peak limit, or any other exposure limit used for the hazardous substance.

Respiratory Hazards physical form present in the workplace is as follows:

Dusts and fibers are solid particles that are formed or generated from solid materials through mechanical processes such as crushing, grinding, drilling, abrading or blasting. Examples are lead, silica, and asbestos.

Fumes are solid particles that are formed when a metal or other solid vaporizes and the molecules condense (or solidify) in cool air. Examples are metal fumes from smelting or welding. Fumes also may be formed from processes such as plastic injection or extrusion molding.

Mists are tiny droplets of liquid suspended in the air. Examples are oil mist produced from lubricants used in metal cutting operations, acid mists from electroplating, and paint spray mist from spraying operations.

Gases are materials that exist as individual molecules in the air at room temperature. Examples are welding gases, such as acetylene and nitrogen, and carbon monoxide produced from internal combustion engines.

Vapors are the gaseous form of substances that are normally in the solid or liquid state at room temperature and pressure. They are formed by evaporation. Most solvents produce vapors. Examples include toluene and methylene chloride.

Biological hazards include bacteria, viruses, fungi, and other living organisms that are respirable and can cause acute and chronic infections. Examples include Legionnaire’s Disease and animal waste products (e.g., feces).

Reference: https://www.osha.gov/Publications/3352-APF-respirators.pdf