Surgical masks, that cover both the nose and the mouth, must be worn by all OHCP during clinical activities likely to generate splash, spatter, spray, and aerosols.1-5 Masks also protect patients from exposure to infectious pathogens carried in the mouth or nose of OHCP. Finally, surgical masks should be worn by coughing patients to limit potential dissemination of infectious respiratory secretions to others, i.e., Respiratory Hygiene/Cough Etiquette.
Surgical masks, which are Class II medical devices, are labeled according to their performance level on testing standards developed by the American Society for Testing and Materials (ASTM). This FDA-accepted testing method (ASTM 2100-11) takes into consideration fluid resistance, bacterial filtration efficiency (BFE), particulate filtration efficiency (PFE), breathability (P-Δ), and flammability of the mask material in determining barrier performance (Table 1).11
|ASTM level||Fluid resistance (mmHg)||BFE (1-5 microns)||PFE (0.1-1.0 microns)||Breathability (P-Δ in mm H2O/cm2||Flammability||Barrier effectiveness level in the presence of splash, spatter, spray, and aerosols|
|1||80||≥ 95%||—||< 4||Class 1||Low|
|2||120||≥ 98%||—||< 5||Class 1||Moderate|
|3||160||≥ 98%||—||< 5||Class 1||High|
|Particulate respirator||160||—||≥ 95%||> 5||Class 1||Airborne Precautions|
Surgical masks are available with fluid-resistant outer layers and tissue inner layers or fluid-resistant outer and inner layers. Fluid resistance helps protect the oral and respiratory mucosa of OHCP from splash, splatter, spray, and aerosols generated during patient care. A mask’s resistance to penetration by synthetic blood under pressure at 80, 120, and 160 mmHg is tested on a pass/fail basis. Surgical masks with higher resistance provide for greater protection.
Bacterial and particulate filtration efficiency reflects the effectiveness of a fabric to filter out bacteria or particles, respectively. The results are expressed as the percentage (%) of bacteria or particles filtered by the fabric. However, even with high filtering efficiency, some inhaled and/or exhaled air can pass unfiltered around the edges of the mask. The greater the edge leakage of a surgical mask, the lower its in-use BFE and PFE.
P-Δ measures the pressure change (in mm H2O/cm2) across the mask, i.e., the resistance to air flow. It is expressed numerically on a scale of 1 to 5. Resistance relates directly to the degree of protection provided by the mask, i.e., greater the resistance to air flow, the better the protection. Unfortunately, resistance relates inversely to breathability. Flammability measures the rate of flame spread in the mask fabric. Minimum acceptable burn rate is 3.5 seconds (Class 1 rating).12
Masks come in various shapes (e.g., molded and non-molded), sizes, and method of attachment (e.g., ties, elastic, ear loops). Several different types of masks should be available in healthcare settings to meet individual needs of personnel. A new surgical mask must be used for each patient. When a mask becomes wet intra-operatively, it must be changed as soon as possible. Surgical masks should not be confused with particulate respirators described below.