Effects of firefighting hood design, laundering and doffing on smoke protection, heat stress and wearability

Figures & data

Figure 1. Boxplots of Total PAH levels (µg/m²) collected from neck skin under different hood designs stratified by doffing method. The box represents the interquartile range (IQR), the horizontal line in each box represents the median, the upper whisker represents the upper fence 1.5 IQR above the 75th percentile, the lower whisker represents the lower fence 1.5 IQR below the 25th percentile, and the dots represent potential outliers.

Box and whisker plot showing neck skin Total PAH from participants wearing different hood designs that include New Knit, New Blocking and Laundered Blocking, grouped by Doffing Methods that include Traditional and Overhead. Median contamination levels decrease from New Knit to New Blocking to Laundered Blocking when Traditional Doffing is used. Neck skin contamination levels are much lower when using the Overhead Doffing method.

Table 1. Total PAH levels (µg/m²) and non-detectable samples (%) collected from neck skin under different hood designs stratified by doffing method.

Hood design	Doffing method	n	Non-detects^A (%)	Median	Mean	Range	Hood design p-value^B
New-Knit (K)	Traditional	12	8.3	123.0	224.0	<LOD–621	0.020
	Overhead	12	25.0	30.5	38.9	<LOD–157
New-Blocking (B)	Traditional	12	25.0	101.0	196.0	<LOD–740
	Overhead	12	58.3	<LOD	21.0	<LOD–71.2
Laundered-Blocking (L)	Traditional	12	16.7	64.6	64.4	<LOD–179
	Overhead	12	50.0	6.3	23.4	<LOD–104

^ALOD ranges for each PAH included in this analysis: acenaphthene = 0.5–3.0 µg, anthracene = 0.5 µg, benzo(a)anthracene = 0.5 µg, benzo(a)pyrene = 0.5 µg, benzo(b)fluoranthene = 0.5 µg, benzo(g,h,i)perylene = 0.5 µg, benzo(k)fluoranthene = 0.5 µg, chrysene = 0.5-0.8 µg, dibenzo(a,h)anthracene = 1.0–2.0 µg, fluoranthene = 0.5–0.6 µg, fluorene = 0.5 µg, indeno(1,2,3-cd)pyrene = 1.0 µg, naphthalene = 0.7–1.0 µg, phenanthrene = 0.5 µg, pyrene = 1.0 µg.

^BAdjusting for doffing method and total air concentrations of PAHs.

Comparison result:.

New-Knit (greater log values) versus New-Blocking: p-value = 0.971.

New-Knit (greater log values) versus Laundered-Blocking: p-value = 0.009 (significantly different).

New-Blocking (greater log values) versus Laundered-Blocking: p-value = 0.016 (significantly different).

Table 2. Comparison of inner/outer shell PAH levels (ng/100 cm² sample) in samples collected from one new knit hood and three new particulate-blocking worn for the same fire trial.

Hood design	Location	n	Non-detects^A(%)	Median	Mean	Range	Location p-value
New- Knit (K)	Inner	3	0	230	490	100–1140	0.2500
	Outer	3	0	1800	1440	560–1970
New- Blocking (B)	Inner	9	100	<LOD^A	<LOD	<LOD	0.0039
	Outer	9	0	1500	2600	570–7710

^ALOD ranges for each PAH included in this analysis: acenaphthene = 100–400 ng, anthracene = 100–400 ng, benzo(a)anthracene = 100–400 ng, benzo(a)pyrene = 100–400 ng, benzo(b)fluoranthene = 100–400 ng, benzo(g,h,i)perylene = 200–600 ng, benzo(k)fluoranthene = 100–400 ng, chrysene = 100–500 ng, dibenzo(a,h)anthracene = 200–700 ng, fluoranthene = 100–400 ng, fluorene = 100–400 ng, indeno(1,2,3-cd)pyrene = 100–500 ng, naphthalene = 100–400 ng, phenanthrene = 100–400 ng, pyrene = 300–900 ng.

Table 3. Physiological responses for simulated firefighting trial in different hood designs and PPE laundering conditions.

Hood design^A	Heart rate (bpm)			Neck skin temp. (°C)		Core temp. (°C)
	Pre-FF	Post-FF	Peak	Pre-FF	Post-FF	Pre-FF	Post-FF	Peak
New-Knit (K)	91 (21)	154 (21)	171 (18)	32.6 (1.5)	34.0 (2.2)	37.2 (0.3)	37.8 (0.3)	38.0 (0.4)
New-Blocking (B)	89 (17)	157 (22)	172 (15)	32.9 (1.1)	34.2 (1.7)	37.2 (0.3)	37.8 (0.4)	38.0 (0.4)
Laundered-Blocking (L)	88 (17)	159 (29)	173 (19)	32.8 (1.5)	34.6 (2.1)	37.1 (0.3)	37.7 (0.3)	37.9 (0.3)

Note. There were no statistically significant differences between the various hood conditions.

^An = 24 except Heart Rate [L (n = 23)] and Core Temperature [K (n = 22), B (n = 23), L (n = 21)].

Table 4. Firefighters reported perceptions of hoods before firefighting (Pre) and after activity (Post).

Measure		Timing	Hood			Statistics
			New-Knit (K)	New-Blocking (B)	Laundered-Blocking (L)	Hood	Hood, Post Hoc	Time	Interaction
Scale (1–7)	Comfort	Pre	6.0 (1.0)	5.8 (1.0)	5.3 (1.0)	p = 0.006; F = 5.47	KvL p = 0.005	p = 0.011; F = 6.89
		Post	6.0 (0.8)	5.5 (1.3)	4.7 (1.6)
	Thermal	Pre	4.8 (1.2)	4.6 (1.2)	4.5 (1.4)			p < 0.001; F = 29.6
		Post	3.9 (1.2)	3.7 (1.3)	3.6 (1.3)
	Moistness	Pre	7.0 (0.2)	6.9 (0.3)	6.9 (0.3)			p < 0.001; F = 100.7
		Post	5.4 (1.1)	5.5 (1.2)	5.3 (1.4)
	Tight	Pre	3.2 (1.0)	4.0 (0.9)	3.8 (1.0)				p = 0.014; F = 4.59
		Post	3.7 (1.0)	3.6 (1.0)	3.5 (1.2)
Scale (1–5)	Hearing reduction	Pre	4.4 (0.7)	4.0 (0.9)	3.8 (1.0)	p = 0.007; F = 5.28	KvL p = 0.026 KvB p = 0.012
		Post	4.5 (0.7)	3.8 (0.8)	3.7 (1.0)
	Heavy/thick	Pre	3.8 (0.9)	3.1 (0.8)	2.6 (0.8)	p < 0.001; F = 11.8	KvL p < 0.001 KvB p = 0.042	p = 0.002; F = 10.4
		Post	4.0 (0.9)	3.4 (0.9)	2.9 (0.8)
	Stiff	Pre	4.5 (0.7)	4.0 (0.9)	3.4 (1.0)	p < 0.001; F = 9.80	KvL p < 0.001
		Post	4.5 (0.9)	4.0 (0.9)	3.6 (1.1)
	Hot	Pre	4.2 (0.8)	4.0 (0.7)	4.0 (0.9)			p < 0.001; F = 20.8
		Post	3.7 (0.7)	3.4 (0.8)	3.5 (0.9)
	Non-breathable	Pre	3.9 (0.7)	3.7 (0.8)	3.3 (0.8)
		Post	3.5 (0.9)	3.6 (0.8)	3.2 (1.0)
	Damp	Pre	4.9 (0.4)	4.8 (0.9)	4.8 (0.5)			p < 0.001; F = 55.2
		Post	3.8 (1.0)	3.8 (0.9)	4.0 (0.9)
	Noisy	Pre	5.0 (0.0)	3.7 (1.0)	3.5 (1.1)	p < 0.001; F = 13.8	KvL p < 0.001 KvB p < 0.001		p = 0.040; F = 3.38
		Post	4.8 (0.7)	3.9 (1.2)	4.0 (1.2)
	Movement reduction	Pre	4.7 (0.6)	4.5 (0.7)	4.5 (0.7)			p = 0.002; F = 10.5
		Post	4.5 (0.8)	4.0 (1.0)	4.1 (1.1)
	Nonstretchy	Pre	4.3 (0.8)	4.2 (0.7)	3.7 (1.2)	p = 0.005; F = 5.82	KvL p = 0.004	p = 0.024; F = 5.32
		Post	4.3 (0.8)	3.8 (1.0)	3.3 (1.3)