Thermophysiological response of Newton manikin equipped with power-assisted filtering device incorporating a full-face mask in hot environment.

One of the most common reasons inducing discomfort in wearing a respirator is an unpleasant local thermal perception. In this study, the effect of a power-assisted filtering device incorporating a full-face mask on the thermophysiological response was investigated by performing tests on a Newton manikin in a climatic chamber, where hot conditions were simulated setting the ambient temperature at 34 °C and the relative humidity at 32%. Two different levels of metabolic rate (1 MET and 3 MET) were considered. Results show that the variation of metabolic rate plays an important role in the heat exchanges with the environment causing different values of the local and global temperatures. At 1 MET the manikin is in thermal balance with the external environment with or without respirator. At 3 MET although the thermoregulation system is very stressed (the rectal temperature Tre increases continuously with or without respirator), the effect of the respirator produces a small decrease of the local and global temperatures and also of the amount of sweat generated by active thermoregulation Swa (reaching its maximum value of 30 g/min when the respirator is not worn). Furthermore, a little amelioration of the face and body sensation and comfort was observed. In any case, wearing the respirator seems not to provide additional thermal load.

Evaluation of performance loss of paraffin oil loaded filtering facepieces.

Penetration measurements through commercially available filtering facepieces were performed with monodisperse DEHS aerosols ranging from 0.03 µm to 0.40 µm (either singly charged or neutralized), before and after 500 mg of paraffin oil loading. The distinct behavior of Coulomb and polarization capture efficiency is studied: as in the case of non loading also in the case of loading 500 mg of paraffin oil, the electrostatic capture mechanisms are mainly due to the Coulomb contribution up to aerosol particle diameter of about 0.10 µm, just when the polarization contribution becomes substantial. Both Coulomb and polarization capture mechanisms are influenced by the presence of 500 mg of paraffin oil, resulting less effective than the oil unloaded case of about 12% and 11%, respectively. By the occupational hygiene point of view, there is a degradation in the filter performance due to oil loading that the user does not realize because there is no remarkable variation in the breathing resistance.

Variation in penetration of submicrometric particles through electrostatic filtering facepieces during exposure to paraffin oil aerosol.

Several studies show the increase of penetration through electrostatic filters during exposure to an aerosol flow, because of particle deposition on filter fibers. We studied the effect of increasing loads of paraffin oil aerosol on the penetration of selected particle sizes through an electrostatic filtering facepiece. FFP2 facepieces were exposed for 8 hr to a flow rate of 95.0 ± 0.5 L/min of polydisperse paraffin aerosol at 20.0 ± 0.5 mg/m(3). The penetration of bis(2-ethylhexyl)sebacate (DEHS) monodisperse neutralized aerosols, with selected particle size in the 0.03-0.40 µm range, was measured immediately prior to the start of the paraffin aerosol loading and at 1, 4, and 8 hr after the start of paraffin aerosol loading. Penetration through isopropanol-treated facepieces not oil paraffin loaded was also measured to evaluate facepiece behavior when electrostatic capture mechanisms are practically absent. During exposure to paraffin aerosol, DEHS penetration gradually increased for all aerosol sizes, and the most penetrating particle size (0.05 µm at the beginning of exposure) shifted slightly to larger diameters. After the isopropanol treatment, the higher penetration value was 0.30 µm. In addition to an increased penetration during paraffin loading at a given particle size, the relative degree of increase was greater as the particle size increased. Penetration value measured after 8 hr for 0.03-µm particles was on average 1.6 times the initial value, whereas it was about 8 times for 0.40-µm particles. This behavior, as well evidenced in the measurements of isopropanol-treated facepieces, can be attributed to the increasing action in particle capture of the electrostatic forces (Coulomb and polarization), which depend strictly on the diameter and electrical charge of neutralized aerosol particles. With reference to electrostatic filtering facepieces as personal protective equipment, results suggest the importance of complying with the manufacturer instructions when it is specified that their use has to be restricted to a single shift.

[Filtering facepieces: effect of oily aerosol load on penetration through the filtering material]. / Facciali filtranti: effetto dell'accumulo di aerosol oleoso sulla penetrazione attraverso il materiale filtrante.

BACKGROUND: Electrostatic filters are widely used in applications requiring high filtration efficiency and low pressure drop. However various studies showed that the penetration through electrostatic filters increases during exposure to an aerosol flow. OBJECTIVES: This study investigates the effects of prolonged exposure to an oily aerosol on the penetration through filtering facepieces available on the market. METHODS: Some samples of FFP1, FFP2 and FFP3 filtering facepieces were exposed for 8 hours consecutively to a paraffin oil polydisperse aerosol. At the end of the exposure about 830 mg of paraffin oil were deposited in the facepiece. RESULTS: All the examined facepieces showed penetration values that increased with paraffin oil load while pressure drop values were substantially the same before and after exposure. The measured maximum penetration values did not exceed the maximum penetration values allowed by the European technical standards, except in one case. According to the literature, 830 mg of oil load in a facepiece is not feasible in workplaces over an eight- hour shift. However, the trend of the penetration versus exposure mass suggests that if the load increases, the penetration may exceed the maximum allowed values. For comparison a mechanical filter was also studied. This showed an initial pressure drop higher than FFP2 filtering facepieces characterized by comparable penetration values. During exposure the pressure drop virtually doubled while penetration did not change. CONCLUSIONS: The increase in penetration with no increase in pressure drop in the analyzed facepieces indicates that it is necessary to comply with the information supplied by the manufacturer that restricts their use to a single shift.