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PubMedDate not supplied

Firing rate interactions among human orbicularis oris motor units.

Groups of human motor units from the same muscle exhibit joint fluctuations in firing rate during voluntary muscle contraction. In an effort to determine whether similar behavior would be observed in a muscle lacking muscle spindles, motor unit firing behavior was examined in the human orbicularis oris inferior (OOI) during mild voluntary effort. Motor unit activity was recorded with a quadrifilar needle inserted in the OOI. Firing occurrences were identified using a motor unit decomposition procedure. Cross-correlation of motor unit firing rates revealed a tendency for motor unit firing rates to covary, although the effect was somewhat more variable than that observed previously in other skeletal muscles. There was also a statistically significant tendency for pairs of motor units to fire at simultaneous or near-simultaneous (+/- 5 ms) intervals (synchronization). Firing rate variability in OOI motor units was not significantly different (p > .05) from that observed in the FDI. Thus, the present results suggest that the common drive of human motor unit activity may not depend on the presence of muscle spindles.

Action Potentials↗
PubMed2001

Acute effect of ethanol on firing patterns of Purkinje cells in the rat cerebellar slice preparation.

This study examined the acute effects of ethanol (EtOH) on the firing patterns of Purkinje cells (PCs) using an intracellular recording in slice preparation of rat cerebellum. The experiments were performed in sagittal cerebellar slices (400 micrometer) of adult Sprague-Dawley rats (80-100g). Ethanol was applied by a bath superfusion with a known concentration expressed as the percentage of solution by volume (v/v) at 0.1, 0.5, 1, 2, and 4%. The result of the Chi-square test illustrated that the firing patterns were altered significantly after EtOH (p=0.007). However, the firing patterns that were altered by EtOH application were not affected by EtOH concentration (p= 0.1296). Among the 54 PCs tested, 30 PCs did not display any spontaneous firing activity and 24 PCs displayed spontaneous spike activity, either spiking in the simple manner (n=14) or cyclicly oscillating (n=10). In the presence of EtOH, 31 PCs were quiet, 22 PCs exhibited simple spiking activity and 1 PC continued to oscillate. Most PCs that displayed spontaneous activity before EtOH application progressively slowed their spike activity after EtOH superfusion. Especially, it was evident that 9 out of 10 oscillating PCs stopped their regular cyclic activity. In addition, 9 out of 14 PCs that displayed simple spike activity ceased to fire after EtOH application. Eleven out of 30 quiet PCs began to fire irregularly after EtOH application and this phenomenon usually occurred with membrane depolarization. EtOH induced spontaneous activity in 36.7% (11/30) of the quiescent PCs. In conclusion, there was differential EtOH sensitivity in the vitro slice preparation. EtOH depressed the endogenously generated spontaneous activity, especially the oscillatory firing activity. In contrast, the silent PCs were excited after EtOH application. Since this differential sensitivity persists in the presence of tetrodotoxin (TTX), it is suggested that this differential sensitivity is peculiar to the PCs.

Animals↗
PubMed1999

Fire ant attacks on residents in health care facilities: a report of two cases.

BACKGROUND: Imported fire ants now infest more than 310 million acres in the United States and Puerto Rico. Colonies have been found in Arizona, California, New Mexico, and Virginia. Available reports suggest that each year, fire ants sting more than 50% of persons in endemic areas, resulting in a variety of medical consequences. OBJECTIVE: To describe fire ant attacks among patients in health care facilities. DESIGN: Case series and literature review. SETTING: Two nursing homes in Mississippi. PATIENTS: Two nursing home residents. MEASUREMENTS: Clinical records to describe clinical sequelae of multiple stings. RESULTS: With the 2 incidents reported here, the total number of reported indoor fire ant attacks on humans since 1989 is 10. Six of the persons attacked, including the 2 nursing home residents described here (who died after the stings), had preexisting neurologic impairment. Eight of the 10 attacks have been reported in the past 4 years. CONCLUSIONS: The presence of fire ants in occupied dwellings indicates the presence of active fire ant colonies in the immediate proximity. Efforts to eradicate these insects should be undertaken immediately, especially if immobile persons are present. These persons should be considered at risk for fire ant attacks as long as the ants are present.

Aged↗
PubMed1999

Short-term effects of fire and competition on growth and plasticity of the yellow pitcher plant, Sarracenia alata (Sarraceniaceae).

Although recurrent fires are widely assumed to reduce competitive interference of plants of pine savannas, rarely has this assumption been tested explicitly. This 2-yr study reports on the interactive effects of fire and neighbors on short-term growth responses and plasticity in allocation patterns of a carnivorous plant, the yellow pitcher plant, Sarracenia alata. This species relies upon pitfall traps (pitchers) to attract and capture insects to obtain nutrients. Neighbors reduced the growth rate of individual ramet transplants (phytometers) in one but not both years of the study. The effect of neighbors on total (i.e., both above- and belowground) productivity of phytometers was not reduced by a winter fire. Neighbors had a greater effect on large plants than on small plants. Although fire did not affect the growth rate of phytometers in the short term, allocation patterns were greatly altered by both neighbors and fire. Allocation to pitchers increased at the expense of belowground organs following fire and in the absence of neighbors at the unburned site. Results of the current study suggest that adult pitcher plants may tolerate competition from neighboring vegetation by reducing allocation to costly pitchers during years without fire.

Journal Article↗
PubMed2000

Impact of correlated synaptic input on output firing rate and variability in simple neuronal models.

Cortical neurons are typically driven by thousands of synaptic inputs. The arrival of a spike from one input may or may not be correlated with the arrival of other spikes from different inputs. How does this interdependence alter the probability that the postsynaptic neuron will fire? We constructed a simple random walk model in which the membrane potential of a target neuron fluctuates stochastically, driven by excitatory and inhibitory spikes arriving at random times. An analytic expression was derived for the mean output firing rate as a function of the firing rates and pairwise correlations of the inputs. This stochastic model made three quantitative predictions. (1) Correlations between pairs of excitatory or inhibitory inputs increase the fluctuations in synaptic drive, whereas correlations between excitatory-inhibitory pairs decrease them. (2) When excitation and inhibition are fully balanced (the mean net synaptic drive is zero), firing is caused by the fluctuations only. (3) In the balanced case, firing is irregular. These theoretical predictions were in excellent agreement with simulations of an integrate-and-fire neuron that included multiple conductances and received hundreds of synaptic inputs. The results show that, in the balanced regime, weak correlations caused by signals shared among inputs may have a multiplicative effect on the input-output rate curve of a postsynaptic neuron, i.e. they may regulate its gain; in the unbalanced regime, correlations may increase firing probability mainly around threshold, when output rate is low; and in all cases correlations are expected to increase the variability of the output spike train.

Action Potentials↗
PubMed2002

Recommendations for prevention and management of fire ant infestation of health care facilities.

The range of imported fire ants now includes most of the southeastern United States, parts of the Southwest, portions of the East and West Coasts, and Puerto Rico. Increasingly, fire ant attacks on patients in health care facilities have been reported. In this paper, we provide recommendations for fire ant control in and around health care facilities that should help prevent building infestation and further attacks. In addition, we provide algorithms detailing fire ant prevention strategies (indoors and outdoors) and patient management after fire ant stings. Physicians in areas endemic for fire ants should be aware of the possibility that patients may be harmed by these insects, and also should be generally familiar with measures used to control fire ants.

Algorithms↗
PubMed1990

Desensitization of muscarinic stimulated hippocampal cell firing is related to phosphoinositide hydrolysis and inhibited by lithium.

The potency and efficacy of a series of muscarinic agonists for stimulation of neuronal firing rate was compared with stimulation of phosphoinositide (PPI) hydrolysis in similar hippocampal slice preparations. Carbachol, muscarine, pilocarpine, arecoline, bethanechol and oxotremorine varied in potency, but stimulated neuronal firing to a similar extent. At higher concentrations, all of the drugs except oxotremorine caused a decrease in firing rate (desensitization). A comparison of the concentration-response curves for PPI hydrolysis and neuronal firing rates showed that desensitization occurred at a threshold level of PPI hydrolysis. Although the concentration of drug that caused the decrease in firing rate was different for each agonist, the level of PPI hydrolysis at the desensitizing concentration was similar, with the exception of oxotremorine. Oxotremorine, the weakest agonist for stimulation of PPI hydrolysis, did not reach this PPI hydrolysis threshold and did not exhibit desensitization. Oxotremorine was also capable of both blocking and reversing the desensitization caused by carbachol. Low concentrations of pirenzepine, an M1 selective muscarinic antagonist, reversed carbachol desensitization. Concentrations of lithium that disrupt the phosphoinositide cycle by preventing recycling of free inositol (Allison, J. H., et al.: Biochem. Biophys. Res. Commun. 71: 664-670, 1976; Hallcher, L. M. and Sherman, W. R.: J. Biol. Chem. 225: 10896-10901, 1980) slowly reversed desensitization. Furthermore, inositol added to the buffer could re-establish desensitization in lithium-treated preparations. These studies suggest that muscarinic desensitization of hippocampal cell firing is related to large increases in phosphoinositide hydrolysis. Muscarinic receptor-stimulated increases in cell firing may be mediated by a subtype or state of muscarinic receptor different from that mediating phosphoinositide hydrolysis and desensitization.

Action Potentials↗
PubMed1989

Responses of substantia nigra pars reticulata neurons to benzodiazepine ligands after acute and prolonged diazepam exposure. II. Modulation of firing rate.

We have examined the effects of chronic (3 week) and acute (1 hr) exposure to diazepam on firing rate responses of reticulata neurons to the inverse agonist methyl-6,7-dimethoxy-4-ethyl-beta-carboline-3-carboxylate (DMCM) and the benzodiazepine antagonist Ro15-1788. The ability of DMCM and Ro15-1788 to alter firing rate were tested in control, chronic diazepam and acute diazepam-treated rats. In controls, DMCM increased firing rate of reticulata neurons. This effect was reversed by Ro15-1788, which had no effect on firing rate when administered alone. In acute and chronic diazepam-treated groups, low doses of DMCM were less effective in increasing firing than in controls. However, the administration of high doses of DMCM to diazepam-treated animals increased firing rates above the rates observed in control animals after the same compounds. Administration of Ro15-1788 also increased reticulata firing rates above control levels in both acute and chronic diazepam-treated groups. The similarity in reticulata responses after chronic (3 week) and acute (1 hr) diazepam treatments suggests that the altered properties of the benzodiazepine ligands observed after chronic exposure could reflect the presence of diazepam. This may indicate that reticulata neurons themselves do not show changes in sensitivity to benzodiazepine ligands after chronic benzodiazepine exposure. We propose that the altered responses to DMCM and Ro15-1788 in diazepam-treated rats reflect a compensatory change which occurs by 1 hr and maintains reticulata activity at a constant level throughout the period of prolonged exposure to the agonist.

Animals↗
PubMed1994

Chloride-dependent potentials and their effects on firing pattern in guinea-pig cingulate cortical neurons.

Intracellular recordings were made from pyramidal neurons in the anterior cingulate cortex layer V of the guinea-pig slice preparation. An oscillation in membrane potential occurred when the membrane was depolarized to a subthreshold level (e.g. -60 mV), and the oscillation triggered repetitive firing. The frequency of the spontaneous firing varied with the membrane potential: frequencies were 2.9 +/- 1.4, 6 +/- 1, 13 +/- 3, and 17 +/- 3 Hz at the membrane potentials of -60, -58, -55, and -40 mV, respectively. Bicuculline (500 nM to 10 microM) increased the firing rate when the membrane potential was kept around threshold level by DC current injection. 2-Hydroxysaclofen and low Cl- (43 mM) also increased the firing rate, but 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulphonate (SITS, 250 microM) did not change the firing rate. Strychnine (1 to 3 microM) had no effect on the spontaneous firing. These results suggest that the firing frequency of cingulate pyramidal neurons is modulated by GABA tonically released by interneurons.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1996

In vitro analysis of optimal stimuli for phase-locking and time-delayed modulation of firing in avian nucleus laminaris neurons.

Neurons of the avian nucleus laminaris (NL) provide a neural substrate for azimuthal sound localization. We examined the optimal stimuli for NL neurons to maintain high discharge rates, reliable phase-locking, and sensitivity to time-delayed stimuli. Whole-cell recordings were performed in chick [embryonic days 19-21 (E19-E21)] NL neurons using an in vitro slice preparation. Variation of membrane properties along the tonotopic axis was examined. Computer-controlled intracellular current injection was used to mimic postsynaptic currents or conductances (PSCs) generated in NL neurons by the firing of nucleus magnocellularis (NM) neurons during acoustic stimulation. At various stimulus frequencies, the effects of varying the number of NM cells and PSC amplitudes on firing rate and phase-locking were examined. During high-frequency stimulation, the greatest firing rate and phase-locking occurred when the protocol contained few NM cells that generated large PSCs. Because the stimulus-evoked unitary PSCs are small, we propose that NM cells fire in synchrony to generate large PSCs. To mimic the arrival of PSCs during binaural stimulation, two stimulus trains were summed at different delays before injection. The firing rate of NL neurons was greatest with zero delay. A delay of half the stimulus period evoked firing that was less than that evoked with a single train. Neurons lacking strong outward rectification exhibited neither reliable phase-locking during high-frequency stimulation nor sensitivity to stimulus delays. These findings suggest that the firing responses of NL neurons are determined primarily by their membrane properties.

Acoustic Stimulation↗
PubMed1996

Opposing actions of androgen and estrogen on in vitro firing frequency of neuronal oscillators in the electromotor system.

The South American knifefish (Apteronotus leptorhynchus), or brown ghost, produces a high-frequency (600-1000 Hz) sinusoidal electric organ discharge (EOD) with males discharging at higher frequencies than females. In addition, each fish has a unique EOD frequency within the frequency range of its gender. The electromotor circuit responsible for EOD production consists of a medullary pacemaker nucleus (PMN) and spinal electromotor neurons (EMNs). In vitro spinal slice recording showed that, similar to the PMN, EMNs fire spontaneously at rates near the EOD frequency of each fish. The persistence of firing 2 weeks after high spinal transaction demonstrated that spontaneous firing rate was intrinsic to the EMNs and was not dependent on presynaptic input. We confirmed that 11-ketotestosterone (11 kT) raised and 17-beta-estradiol (E2) lowered the EOD frequency of intact fish. Because electromotor cells fire spontaneously near EOD, frequency, we investigated whether these steroids affect endogenous firing rates. Steroid implants were made in normal or spinally transected fish. Two weeks later, PMNs of normal fish and EMNs of transected fish were recorded in vitro. 11 kT increased and E2 decreased the intrinsic firing rate of neurons in the PMN and the EMNS. Hormones shifted the intrinsic firing rates of EMNS, although they were synaptically isolated during the hormone exposure.

Androgens↗
PubMed1996

Ionic currents underlying developmental regulation of repetitive firing in Aplysia bag cell neurons.

We have investigated the developmental regulation of the ability to fire repetitively in the bag cell neurons of Aplysia californica, a neuronal system in which the behavioral effects of repetitive firing are well characterized. Adult bag cell neurons exhibit an afterdischarge, consisting of prolonged depolarization and repetitive firing, which causes the release of several peptides from these neurons that induce egg-laying behaviors. Afterdischarge can be triggered in vitro by a variety of stimuli, including electrical stimulation and exposure to the potassium channel blocker tetraethyl ammonium chloride (TEA). In contrast to adults, juvenile neurons did not exhibit afterdischarge in response to pleural-abdominal connective shock or TEA. Juvenile neurons did exhibit, however, prolonged depolarizations in the presence of TEA, perhaps reflecting the anlage of the mechanism responsible for afterdischarge in the adult. To investigate developmental mechanisms underlying the regulation of repetitive firing, we compared ionic currents in adult and juvenile bag cell neurons. We found that during the period in which these neurons acquire the capacity to fire repetitively, a number of currents are regulated: (1) three K+ currents decrease (Ca2+)-dependent K+ and two components of voltage-dependent delayed-rectifier K+ current); (2) A-type K+ current increases; and (3) two Ca2+ currents increase (basal and PKC-activated). This pattern is consistent with the increase in the ability to fire repetitively that we observe during maturation: our results indicate that developmental control of repetitive firing in this system is accompanied by selective regulation of specific ionic currents which, after maturation, play important roles in generating the afterdischarge and triggering egg-laying behaviors.

Animals↗
PubMed1997

Trans-2-en-valproic acid limits action potential firing frequency in mouse central neurons in cell culture.

Effects of the trans-isomer of 2-en-valproate (trans-2-en-NaVP; E-delta2-en-valproate or 2-en-valproate), an unsaturated metabolite of valproic acid (VPA), on intracellularly recorded sodium-dependent action potentials of cultured mouse spinal cord and cortical neurons were compared with those of the anticonvulsant sodium valproate (NaVP). The maximal rate of rise of action potentials triggered by trains of 1-msec or 400-msec pulses declined progressively until failure to fire in both cell types during exposure to trans-2-en-NaVP or NaVP was observed. The limitation of firing by both drugs was concentration, voltage, rate and time dependent. The IC50 of trans-2-en-NaVP was 1.2 x 10(-3) at < or =1 hr and 4.8 x 10(-5) M at 24 to 48 hr. Trans-2-en-NaVP did not limit sustained repetitive firing in all cortical neurons. This may reflect slower rates of firing during 400-msec depolarizations in neurons of this type. In paired-pulse experiments, the absolute refractory period was 7 msec in control solution and 15 msec (P < .01 vs. control; n = 9) in solution containing 6 x 10(-4) M trans-2-en-NaVP. Firing was limited in all spinal cord neurons after exposure to 0.5 mM NaVP for 24 to 48 hr; 80% were limited by 1 mM NaVP at < or =1 hr. Coincubation of the spinal cord neurons with trans-2-en-NaVP and NaVP for 24 hr showed no hyperadditive effect of these two drugs in vitro. Limitation of sustained repetitive firing was reversed by hyperpolarization in the continuing presence of either drug and incubation in drug-free medium. Limitation of sodium-dependent action potential firing rates could contribute, at least in part, to the anticonvulsant effect of trans-2-en-NaVP.

Action Potentials↗
PubMed1997

Firing properties of head direction cells in the rat anterior thalamic nucleus: dependence on vestibular input.

Vestibular information influences spatial orientation and navigation in laboratory animals and humans. Neurons within the rat anterior thalamus encode the directional heading of the animal in absolute space. These neurons, referred to as head direction (HD) cells, fire selectively when the rat points its head in a specific direction in the horizontal plane with respect to the external laboratory reference frame. HD cells are thought to represent an essential component of a neural network that processes allocentric spatial information. The functional properties of HD cells may be dependent on vestibular input. Here, anterior thalamic HD cells were recorded before and after sodium arsanilate-induced vestibular system lesion. Vestibular lesions abolished the directional firing properties of HD cells. The time course of disruption in the directional firing properties paralleled the loss of vestibular function. Arsanilate-treated rats exhibited only minor changes in locomotor behavior, which were unlikely to account for the loss of direction-specific firing. Vestibular lesions also disrupted the influence of angular head velocity on anterior thalamic single-unit firing rates. Finally, a subset of anterior thalamic neurons recorded from vestibular-lesioned rats exhibited a pattern of intermittent firing bursts that were distinctly unrelated to HD. This novel anterior thalamic firing pattern has not been encountered in any vestibular-intact rat. These data suggest that: (1) the neural code for directional bearing is critically dependent on vestibular information; and (2) this loss of HD cell information may represent a neurobiological mechanism to account for the orientation and navigational deficits observed after vestibular dysfunction.

Action Potentials↗
PubMedDate not supplied

Evidence that the firing pattern of sympathetic preganglionic neurones is determined by an interaction between amines and an excitatory amino acid.

Extracellular recordings were made from identified sympathetic preganglionic neurones (SPN) located in the second and third thoracic segments of the adult rat spinal cord, in-vivo. Iontophoretic application of the amines, 5-hydroxytryptamine (5-HT) and noradrenaline (NAdr) in the vicinity of these neurones evoked either long lasting excitations, inhibitions or bi-phasic changes (inhibition followed by excitation, 5-HT only) in neuronal firing rate. The excitatory response to both 5-HT or NAdr could only be obtained in spontaneously active neurones, or silent neurones, in which a subliminal level of an excitatory amino acid (EAA) was also present. In 4 neurones, the response evoked by NAdr was dependent on neuronal firing rate and hence the level of EAA present. At low basal firing rates, inhibitions were observed whereas at higher firing rates, excitations were observed. Subliminal levels of either 5-HT or NAdr markedly potentiated the increases in neuronal firing rate evoked by an EAA. In a sub-population of SPN, both 5-HT (18/88 neurones) and NAdr (21/51 neurones) induced a repeated bursting pattern of action potential discharge during the amine evoked changes in neuronal firing rate in otherwise irregularly discharging neurones. We conclude that these actions of the monoamines, that is excitations or inhibitions, gain enhancement, prolongation of action, burst firing and oscillations are likely to be due to the modulation by these agents of intrinsic membrane conductances. The differing responses evoked in SPN will produce marked differences in the efficacy of synaptic transmission in the sympathetic ganglia. As a result of these mechanisms, there will be a greater versatility in the sympathetic control systems than would otherwise exist.

Animals↗
PubMed1998

The differential expression of low-threshold sustained potassium current contributes to the distinct firing patterns in embryonic central vestibular neurons.

The principal cells of the chick tangential nucleus are second-order sensory neurons that participate in the three-neuron vestibulo-ocular and vestibulocollic reflexes. In postnatal animals, second-order vestibular neurons fire repetitively on depolarization. Previous studies have shown that, although this is an important feature for normal reflex function, it is only acquired gradually during embryonic development. Whereas at 13 embryonic days (E13) the principal cells accommodate after firing a single spike, at E16 a few principal cells repetitively can fire multiple action potentials on depolarization. Finally, in the hatchling, the vast majority of principal cells is capable of nonaccommodating firing on depolarization. As a first step in understanding the mechanisms underlying developmental change in excitability of these second-order vestibular neurons, we analyzed the outward potassium currents and their role in accommodation, using brainstem slices at E16. The principal cells exhibited transient and sustained potassium currents, with both of these containing calcium-dependent components. Further, both high- and low-threshold sustained potassium currents have been distinguished. The low-threshold dendrotoxin-sensitive sustained potassium current (IDS) is associated with principal cells that accommodate and is not expressed in those that fire repetitively. Finally, blocking of IDS transforms accommodating cells into neurons capable of firing trains of action potentials on depolarization. These findings indicate that suppression of IDS during development is sufficient to transform accommodating principal cells into nonaccommodating firing neurons and suggests that developmental regulation of this current is necessary for the establishment of normal vestibular function.

Action Potentials↗
PubMed2001

Is testicular cancer an occupational disease of fire fighters?

BACKGROUND: A previous investigation showed an increased risk of testicular cancer among fire fighters in Wellington City, New Zealand, during the 1980s. Other studies of fire fighters had not identified testicular cancer as an occupational disease. METHODS: This was an historical cohort study of mortality and cancer incidence in all paid New Zealand fire fighters, from 1977 to 1995. RESULTS: The only cancer for which this study provided evidence of an increased risk was testicular cancer, even after excluding cases from the previous investigation. The standardized incidence ratio for 1990-96 was 3.0 (95% confidence interval: 1.3-5.90). There was no evidence that fire fighters were at increased risk from any particular cause of death. CONCLUSIONS: This study confirmed that New Zealand fire fighters are at increased risk of testicular cancer, although the reason is unknown. Other incidence studies of cancer in fire fighters are needed to confirm this finding.

Adult↗
PubMed2006

Effect of protective filters on fire fighter respiratory health during simulated bushfire smoke exposure.

BACKGROUND: Bushfire fighters are potentially subject to risks from bushfire smoke. Although many different protective masks and filters are available, it is not clear which is the most effective from a health and safety perspective. The effect of protective filters on the respiratory health of Western Australian urban career fire fighters under controlled simulated conditions is investigated. METHODS: Sixty-four healthy Fire and Emergency Services Authority of Western Australia (FESA) urban career fire fighters were subjected to controlled simulated bushfire smoke in an open smoke chamber for 15 min. The fire fighters were allocated one of the three types of protective filters: particulate only (P), particulate/organic vapor (POV), and a particulate/organic vapor/formaldehyde (POVF) filter using a double-blind randomized procedure. Personal air sampling inside the fire fighters' masks, spirometry, oximetry, and self-reported symptom data were collected at baseline and at two time intervals after the smoke exposure. RESULTS: A significant decline in oxygen saturation was seen immediately after exposure, however, the decline was small and no significant relationships could be established between this and the type of filter used. A significantly higher number of participants in the P and POV filter groups self-reported an increase in coughing, wheezing, and shortness of breath compared to the POVF group. Air sampling demonstrated a significantly higher level of formaldehyde and acrolein inside the masks fitted with P filters compared to POV and POVF filters. CONCLUSIONS: Testing the effectiveness of P, POV, and POVF filters under controlled conditions has demonstrated that the POVF filter provides statistically significant better protection for the fire fighters' airways in a simulated bushfire exposure chamber.

Adult↗