A pilot study of minimum operational flow for loose-fitting powered air-purifying respirators used in healthcare cleaning services.

The objective of this pilot study was to determine the minimum operational flow for loose-fitting powered air-purifying respirators (PAPR) used in healthcare cleaning services. An innovative respiratory flow recording device was worn by nine healthcare workers to obtain the minute volume (MV, L/min), mean inhalation flow (MIF, L/min), and peak inhalation flow (PIF, L/min) while performing "isolation unit work" (cleaning and disinfecting) of a patient room within 30 min. The MV and PIF were compared with the theoretical values obtained from an empirical formula.

Assessment of Two Personal Breathing Recording Devices in a Simulated Healthcare Environment.

Background: In the field of respiratory protection for healthcare workers (HCWs), few data are available on respiratory airflow rate when HCWs are performing their work activities. The objective of this study was to assess the performance of two wearable breathing recording devices in a simulated healthcare environment.

Methods: Breathing recording devices from two different manufactures "A" and "B" were assessed using 15 subjects while performing a series of simulated healthcare work activities (patient assessment; vitals; IV treatment; changing linen; carrying weight while walking; normal breathing while standing).

Experimental study on centerline velocities of a rectangular capture hood under realistic conditions.

Capture hoods are an important component of a local ventilation system designed to reduce exposures to airborne contaminants. The velocity at any point along the centerline of the hood (V) is currently estimated using one of many predictive equations developed since the 1930s. It is unproven that those predictive equations for V are accurate, despite the prodigious number of studies concerning them.

Comparison between active (pumped) and passive (diffusive) sampling methods for formaldehyde in pathology and histology laboratories.

This study was to determine occupational exposures to formaldehyde and to compare concentrations of formaldehyde obtained by active and passive sampling methods. In one pathology and one histology laboratories, exposure measurements were collected with sets of active air samplers (Supelco LpDNPH tubes) and passive badges (ChemDisk Aldehyde Monitor 571). Sixty-six sample pairs (49 personal and 17 area) were collected and analyzed by NIOSH NMAM 2016 for active samples and OSHA Method 1007 (using the manufacturer's updated uptake rate) for passive samples.

Quantitative evaluation of the performance of an industrial benchtop enclosing hood.

Plain benchtop enclosing hoods are assumed to be highly effective in protecting workers from airborne contaminants, but there is little research published to support or rebut that assumption. The purpose of this research was to investigate the performance of a 36 in. wide, 30 in.

Flow dynamics and contaminant transport in industrial-type enclosing exhaust hoods.

The present study concerns the flow dynamics and associated contaminant transport in the near wake of a worker using an industrial-type benchtop enclosing hood. The primary focus is on evaluating the effects on the dynamics of the wake flow and the exposure level of various extraneous factors, such as the strength and direction of cross-drafts and the worker's body heat and shape. Three-dimensional Unsteady Reynolds-Averaged Navier-Stokes simulations were carried out for a model of a simple mannequin and a model of an anthropometric mannequin.

Experimental validation of a target method for balancing exhaust ventilation duct systems with dampers.

This study tested the "Target Method" for adjusting ventilation systems. The Target Method is based on target hood static pressures (SPh(target)) computed in a manner designed to take into account the estimated effects of dampers on the fan, the order of damper adjustments, and the ratio of the prebalancing branch airflows to their goals. It is aimed at achieving a desired relative distribution of airflows even if the fan output is far from ideal.

Effects of cross-sectional partitioning on active noise control in round ducts.

Active noise control (ANC) is particularly useful in hard-walled ducts where plane waves propagate. Higher order mode waves are much more difficult to control. Basic acoustic principles dictate that the cut-on frequency at which higher order modes will first begin to eclipse simple plane waves in a duct will be determined by the cross-sectional diameter of the duct.

Effects of cross-sectional dimensions on active noise control in rectangular and round ducts.

Active noise control (ANC) works best to reduce low frequency noise. Because many industrial noise sources are broadband, ANC may be used more if it can be successfully applied to higher frequency ranges. This study explored one method to increase ANC effectiveness at higher frequencies.

A Goal Method and a Target Method for balancing exhaust ventilation duct systems with dampers.

This work presents and discusses two approaches to adjusting dampers, here called the Goal and Target Methods. A form of the Goal Method is commonly employed but has not been clearly described or discussed elsewhere. The Target Method is a novel variation of so-called "proportional" methods.

A numerical study of worker exposure to a gaseous contaminant: variations on body shape and scalar transport model.

Three-dimensional computational fluid dynamics simulations are used to investigate the distribution and level of contaminant concentrations in the true breathing zone (at the nose and mouth) when toxic airborne contaminants are released within an arm's length in front of the worker who has his back to the airflow. The effects of different body shapes on fluid flow and concentration patterns around the body in a wind tunnel were evaluated and clarified that a sharp body or a block may not be a good surrogate for the human form in consideration of occupational and environmental health studies. The comparison of the concentration field calculated with the Eulerian and Lagrangian methods revealed that the Eulerian method has a more diffusive nature than the Lagrangian method.

Applying open-path FTIR with computed tomography to evaluate personal exposures. Part 1: simulation studies.

This paper presents the theoretical background and the numerical evaluation results obtained using computed tomography coupled with open-path Fourier transform infrared (CT-FTIR) measurements to estimate personal exposures. In this simulation study, we first tested the one-dimensional scenario with a five-beam segment geometry. A series of Gaussian plumes and the corresponding path-integrated concentrations (PICs) were simulated.

Field evaluation of methods for determining the obstructed section of branches of industrial ventilation systems.

This study proposes and evaluates the effectiveness of three methods in determining the location of obstructions and alterations in the branches of industrial ventilation systems. Three branch-screening methods (reference ratio, static pressure ratio, and power loss coefficient methods) were adapted to determine if obstructions lay in four distinct areas of a branch. The areas were the hood, middle, and end sections, with the middle and end sections combined to form the fourth area.

The effect of local exhaust ventilation controls on dust exposures during concrete cutting and grinding activities.

This study assessed the effectiveness of commercially available local exhaust ventilation (LEV) systems for controlling respirable dust and crystalline silica exposures during concrete cutting and grinding activities. Work activities were performed by union-sponsored apprentices and included tuck-point grinding, surface grinding, paver block and brick cutting (masonry saw), and concrete block cutting (hand-held saw). In a randomized block design, implemented under controlled field conditions, three ventilation rates (0, 30, and 75 cfm) were tested for each tool.