2015-03-01 12:00 - Messages

Experimental and modeling study of thermal exposure of a self-contained breathing apparatus (SCBA)

An experimental apparatus designed to study firefighter safety equipment exposed to a thermal environment was developed. The apparatus consisted of an elevated temperature flow loop with the ability to heat the air stream up to 200°C. The thermal and flow conditions at the test section were characterized using thermocouples and bi-directional probes. The safety equipment examined in this study was a self-contained breathing apparatus (SCBA), including a facepiece and an air cylinder. The SCBA facepiece was placed on a mannequin headform and coupled to a breathing simulator that was programmed with a prescribed breathing pattern. The entire SCBA assembly was placed in the test section of the flow loop for these thermal exposure experiments. Three air stream temperatures, 100°C, 150°C, and 200°C, were used with the average air speed at the test section set at 1.4m/s and thermal exposure durations up to 1200s. Measurements were made using type-K bare-bead thermocouples located in the mannequin's mouth and on the outer surface of the SCBA cylinder. The experimental results indicated that increasing the thermal exposure severity and duration increased the breathing air temperatures supplied by the SCBA. Temperatures of breathing air from the SCBA cylinder in excess of 60°C were observed over the course of the thermal exposure conditions used in most of the experiments. A mathematical model for transient heat transfer was developed to complement the thermal exposure experimental study. The model took into consideration forced convective heat transfer, quasi-steady heat conduction through the composite layers of the SCBA cylinder wall, the breathing pattern and action of the breathing simulator, and predicted air temperatures from the thermally exposed SCBA cylinder and temperatures at the outer surface of the SCBA cylinder. Model predictions agreed reasonably well with the experimental measurements.

Source: Donnelly MK, Yang JC. Burns, 2015.

Perceived risks for slipping and falling at work during wintertime and criteria for a slip-resistant winter shoe among Swedish outdoor workers

The leading cause of work related accidents in Sweden is falls. Many slips and falls occur on icy and snowy surfaces, but there is limited knowledge about how to prevent accidents during outdoor work in winter conditions. The purpose of this study was to describe risk factors of slips and falls and criteria for slip-resistant winter shoes from a user perspective. The result is based on focus group interviews with 20 men and women working in mail delivery, construction and home care in Sweden. The data was analyzed with qualitative content analysis. Risk factors described were related to physical work environment, risky work situations, individual and organizational factors. User criteria for winter work shoes focused on safety, adaptation to the environment, usability and own priorities. The mechanisms of slips and falls during outdoor work are complex. There is a need for more functional and user friendly work shoes than those available and user preferences should be considered by shoe designers. Future challenges include finding ways to make individually adapted shoes suitable for changing work environments, situations and tasks.

Source: Norlander A, Miller M, Gard G. Safety Sci. 2015; 73: 52-61.

Effect of firefighters' personal protective equipment on gait

The biomechanical experiment with eight male and four female firefighters demonstrates that the effect of adding essential equipment: turnout ensemble, self-contained breathing apparatus, and boots (leather and rubber boots), significantly restricts foot pronation. This finding is supported by a decrease in anterior-posterior and medial-lateral excursion of center of plantar pressure (COP) trajectory during walking. The accumulation of this equipment decreases COP velocity and increases foot-ground contact time and stride time, indicating increased gait instability. An increase in the flexing resistance of the boots is the major contributor to restricted foot pronation and gait instability as evidenced by the greater decrease in excursion of COP in leather boots (greater flexing resistance) than in rubber boots (lower resistance). The leather boots also shows the greatest increase in foot contact time and stride time. These negative impacts can increase musculoskeletal injuries in unfavorable fire ground environments.

Source: Park H, Kim S, Morris K, Moukperian M, Moon Y, Stull. J. Appl. Ergon, 2015; 48: 42-48.

Effects of air bottle design on postural control of firefighters

The purpose of this study was to investigate the effect of firefighter's self-contained breathing apparatus (SCBA) air bottle design and vision on postural control of firefighters. Twenty-four firefighters were tested using four 30-minute SCBA bottle designs that varied by mass and size. Postural sway measures were collected using a forceplate under two visual conditions (eyes open and closed) and two stance conditions (quiet and perturbed stances). For perturbed stance, a mild backward impulsive pull at the waist was applied. In addition to examining center of pressure postural sway measures for both stance conditions, a robustness measure was assessed for the perturbation condition. The results suggest that wearing heavy bottles significantly increased excursion and randomness of postural sway only in medial-lateral direction but not in anterior-posterior direction. This result may be due to stiffening of plantar-flexor muscles. A significant interaction was obtained between SCBA bottle design and vision in anterior-posterior postural sway, suggesting that wearing heavy and large SCBA air bottles can significantly threaten postural stability in AP direction in the absence of vision. SCBA bottle should be redesigned with reduced weight, smaller height, and COM closer to the body of the firefighters. Firefighters should also widen their stance width when wearing heavy PPE with SCBA.

Source: Hur P, Park K, Rosengren KS, Horn GP, Hsiao-Wecksler ET. Appl. Ergon. 2015; 48: 49-55.

Do active safety-needle devices cause spatter contamination?

Exposure to blood and body fluids is an occupational hazard in healthcare. Although the potential for blood-borne virus transmission through needlestick injury has been widely studied, the risk of this occurring through spatter contamination from safety-needle syringes is not well understood. This report examines this risk from three commonly used safety needles and suggests that this presents a new and significant hazard. Further work should be commissioned to quantify this hazard and determine which type of safety needle would minimize spatter contamination following syringe discharge and safety activation.

Source: M. Roffa, S. Basub, A. Adiseshc. Journal of Hospital Infection, Volume 86, Issue 3, March 2014, p. 221–223.

Review of fit test pass criteria for Filtering Facepieces Class 3 (FFP3) respirators

Respiratory Protective Equipment (RPE) is available in a range of types which often include a tight-fitting facepiece which must fit the wearer's face well for the RPE to work effectively. Good fit must be demonstrated by fit testing.
In this study, 25 volunteer test subjects wearing tight-fitting FFP3 (randomly selected from 9 different models) underwent four fit tests (Bitrex qualitative taste test, Portacount particle counting with and without the N95 companion technology and the laboratory chamber method), in random order, according to methodology given in HSE guidance 282/28. The selected FFP3 model worn by each test subject was not adjusted until all four fit tests had been completed.
Results analysed according to the criteria given in the American National Standard for fit test validation, indicate that the Portacount fit test method is more difficult to pass than the other methods. Differences in the methodologies and the potential for bias in the results across the fit test methods are discussed.

Source: http://www.hse.gov.uk/research/rrhtm/rr1029.htm

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