Evaluation of properties of elastomeric head straps of filtering facepiece respirators

Figures & data

Figure 1. Design of the typical filtering facepiece respirator. Note: 1 = nose clip; 2 = elastomeric head straps; 3 = exhalation valve; 4 = inner seal; 5 = filtering material (filtering facepiece). The full colour version of this figure is available online.

Figure 2. Types of elastomeric tapes used in design of the filtering facepiece respirator (FFR). Note: 1 = round thin; 2 = round large; 3 = wide rectangular; 4 = narrow rectangular; 5 = ordinary.

Table 1. Technical specifications of elastomeric tapes.

Elastomeric strap sample number	Country of manufacturer	Composition of raw materials (%)	Width (mm)	Breaking force (N)	Surface density (g / m^2)	Maximum elongation (%)
1	China	PE 39, el. thread 10.6, PP 50.2	4	35	120	125
2	Ukraine	PE 76.7, el. thread 23.3	5	43	153	92
3	China	PE 63.3, el. thread 36.7	10	82	220	74
4	Belorussia	PE 68.2, el. thread 31.8	5	57	175	85
5	Poland	PE 69.6, el. thread 30.4	7	63	183	81

Note: 1 = round thin; 2 = round large; 3 = wide rectangular; 4 = narrow rectangular; 5 = ordinary; PE = polyethylene; PP - polypropylene.

Figure 3. General view of laboratory tests. Note: 1 = respirator model Standard 213 FFP2 NR (LLC SPE Standart, Ukraine); 2 = elastomeric head straps; 3 = dynamometer DU-100 (PromTechniMashPrylad, Ukraine); 4 = differential pressure gauge Testo 512 (TESTO AG, Germany). The full colour version of this figure is available online.

Figure 4. Dependence of relative elongation, Δl / l (%), of elastomeric straps on tension force, F_T (N). Note: 1 = round thin; 2 = round large; 3 = wide rectangular; 4 = narrow rectangular; 5 = ordinary. The full colour version of this figure is available online.

Table 2. Elongation of elastomeric head straps due to repeated donning and doffing of the FFR.

	Elastomeric strap elongation, Δl / l (mm)/tensile strength, Fn (N), during the donning and doffing procedure
Elastomeric strap number	1 time	3 times	5 times	8 times	10 time	Relative elongation of elastomeric strap at end of the experiment (%)
1	5.1 ± 0.3	12.3 ± 0.8	17.5 ± 0.7	18.2 ± 0.4	18.6 ± 0.6	76
	/9.3 ± 0.5	/9.2 ± 0.4	/9.3 ± 0.4	/9.5 ± 0.7	/9.1 ± 0.3
2	1.6 ± 0.5	3.2 ± 0.4	3.6 ± 0.5	4.1 ± 0.3	4.2 ± 0.4	68
	/8.4 ± 0.5	/8.3 ± 0.5	/8.5 ± 0.5	/8.4 ± 0.5	/8.3 ± 0.5
3	0.8 ± 0.4	1.1 ± 0.3	1.3 ± 0.4	1.5 ± 0.5	1.5 ± 0.5	35
	/6.2 ± 0.4	/6.1 ± 0.4	/6.2 ± 0.4	/6.6 ± 0.5	/6.4 ± 0.4
4	1.2 ± 0.4	1.5 ± 0.5	1.9 ± 0.3	2.1 ± 0.3	2.2 ± 0.4	41
	/7.1 ± 0.3	/7.2 ± 0.3	/7.1 ± 0.3	/7.2 ± 0.4	/7.2 ± 0.4
5	1.1 ± 0.3	1.4 ± 0.5	1.6 ± 0.5	1.8 ± 0.4	1.8 ± 0.4	38
	/6.7 ± 0.5	/6.8 ± 0.4	/6.7 ± 0.5	/6.5 ± 0.5	/6.6 ± 0.5

Note: Data presented as mean ± standard deviation. FFR = filtering facepiece respirator. 1 = round thin; 2 = round large; 3 = wide rectangular; 4 = narrow rectangular; 5 = ordinary.

Table 3. Residual tensile strength of elastomeric head straps after multiple procedures of donning and doffing the FFR.

			Residual tension force of elastomeric straps, Fn (N), after subsequent donning and doffing
Elastomeric strap number	Initial tension force, F0n (N)	Maximum fixed tensile strength, Fmax (N)	1 time	3 times	5 times	8 times	10 times
1	4.5 ± 0.14	9.5	4.2 ± 0.5	3.6 ± 0.4	2.5 ± 0.2	2.1 ± 0.2	1.9 ± 0.5
2	4.9 ± 0.18	8.5	4.9 ± 0.1	4.3 ± 0.6	3.8 ± 0.6	3.5 ± 0.3	3.2 ± 0.5
3	5.3 ± 0.19	6.6	5.3 ± 0.1	5.2 ± 0.5	5.1 ± 0.3	5.0 ± 0.5	5.0 ± 0.1
4	4.7 ± 0.15	7.2	4.7 ± 0.2	4.4 ± 0.5	3.9 ± 0.4	3.6 ± 0.5	3.5 ± 0.1
5	5.2 ± 0.10	6.8	5.2 ± 0.1	5.1 ± 0.4	4.8 ± 0.5	4.6 ± 0.1	4.5 ± 0.5

Note: Data presented as mean ± standard deviation. FFR =filtering facepiece respirator. 1 = round thin; 2 = round large; 3 = wide rectangular; 4 = narrow rectangular; 5 = ordinary.

Table 4. Pressure drops on the FFR due to multiple donning and doffing cycles.

		Pressure drop on the FFR due to multiple donning and doffing cycles, Δpr (Pa)
Elastomeric strap number	Initial pressure drop on the FFR, Δpf (Pa)	1 time	3 times	5 times	8 times	10 times
1	75.2	73.2 ± 1.1	70.3 ± 1.3	68.5 ± 1.1	64.3 ± 1.5	60.2 ± 1.5
2	75.3	74.3 ± 1.1	72.4 ± 1.2	70.8 ± 1.2	68.2 ± 1.3	65.4 ± 1.4
3	75.4	74.6 ± 0.9	73.5 ± 1.2	72.5 ± 1.3	71.5 ± 1.1	70.2 ± 1.2
4	75.4	74.3 ± 1.05	72.6 ± 1.1	70.5 ± 1.3	68.2 ± 1.2	66.5 ± 1.1
5	75.2	74.4 ± 1.2	73.9 ± 0.9	72.3 ± 1.2	70.2 ± 1.3	68.4 ± 1.3

Note: Data presented as mean ± standard deviation. FFR =filtering facepiece respirator. 1 = round thin; 2 = round large; 3 = wide rectangular; 4 = narrow rectangular; 5 = ordinary.

Table 5. Changes in protection factor due to multiple donning and doffing cycles for different elastomeric tapes.

		Protection factor after multiple donning and doffing cycles (%)
Elastomeric strap number	Initial protection factor of the FFR (%)	1 time	3 times	5 times	8 times	10 times
1	98.6 ± 0.42	97.9 ± 0.21	95.6 ± 0.53	94.3 ± 0.28	92.3 ± 0.28	90.5 ± 0.91
2	98.8 ± 0.21	98.4 ± 0.17	95.9 ± 0.35	95.7 ± 0.42	94.8 ± 0.23	93.6 ± 0.40
3	98.9 ± 0.17	98.5 ± 0.25	96,3 ± 0.21	95.9 ± 0.29	95.5 ± 0.32	95,0 ± 0.53
4	98.7 ± 0.24	98.4 ± 0.14	96.0 ± 0.37	95.1 ± 0.21	94.2 ± 0.28	93.5 ± 0.54
5	98.9 ± 0.31	98.4 ± 0.32	96.5 ± 0.15	95.8 ± 0.21	95.0 ± 0.17	94.3 ± 0.29

Note: Data presented as mean ± standard deviation. FFR = filtering facepiece respirator. 1 = round thin; 2 = round large; 3 = wide rectangular; 4 = narrow rectangular; 5 = ordinary.

Figure 5. General view of laboratory tests of a respirator with a modernized headband: (a) general view; (b) side view; (c) back view. Note: 1 = respirator model Standard 213 FFP2 NR (LLC SPE Standart, Ukraine); 2 = elastomeric head straps; 3 = dynamometer DU-100 (PromTechniMashPrylad, Ukraine); 4 = plastic insert. The full colour version of this figure is available online.

Table 6. Changes in protection factor due to multiple donning and doffing cycles.

					FFR’s protection factor after multiple donning and doffing procedures (%)
Strap length (mm)	Initial protection factor (%)	Initial fixed tensile force/maximal fixed tensile force (N)	Length of plastic insert (mm)	Relative elongation of straps at the test end (%)	3 times	5 times	8 times	10 times
100	98.4	5.7/11.8	100	22.1	98.5	98.3	98.1	98.0
120	98.5	5.4/10.2	100	26.3	98.6	98.4	97.9	97.7
140	98.4	5.1/10.1	100	30.6	98.5	98.2	97.5	97.4

Note: FFR = filtering facepiece respirator.