A Comparison between Temperature-Controlled Laminar Airflow Device and a Room Air-Cleaner in Reducing Exposure to Particles While Asleep

Abstract

People spend approximately one third of their life sleeping. Exposure to pollutants in the sleep environment often leads to a variety of adverse health effects, such as development and exacerbation of asthma. Avoiding exposure to these pollutants by providing a sufficient air quality in the sleep environment might be a feasible method to alleviate these health symptoms. We performed full-scale laboratory measurements using a thermal manikin positioned on an experimental bed. Three ventilation settings were tested: with no filtration system operated, use of portable air cleaner and use of a temperature-controlled laminar airflow (TLA) device. The first part of the experiment investigated the air-flow characteristics in the breathing zone. In the second part, particle removal efficiency was estimated. Measured in the breathing zone, the room air cleaner demonstrated high turbulence intensity, high velocity and turbulence diffusivity level, with a particle reduction rate of 52% compared to baseline after 30 minutes. The TLA device delivered a laminar airflow to the breathing zone with a reduction rate of 99.5%. During a periodical duvet lifting mimicking a subject's movement in bed, the particle concentration was significantly lower with the TLA device compared to the room air cleaner. The TLA device provided a barrier which significantly reduced the introduction of airborne particles into the breathing zone. Further studies should be conducted for the understanding of the transport of resuspended particles between the duvet and the laying body.

Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1. Experimental chamber setup.

Fig 2. Experimental setup of the TLA device.

Fig 3. Results from 3D air velocity measurements at 8 cm above the nose tip.

The results are presented in terms of orthogonal air velocity components (Ux, Uy, Uz) and the airflow.

Fig 4. The airflow velocity vectors determined under the TLA cooled air supply nozzle.

Displayed are measured positions: 23 cm above the nose tip (X = 0, Y = 0, Z = 0.23m), 8 cm above the nose tip (X = 0, Y = 0, Z = 0.08m), right and left side of the face (X = 0, Y = ±0.2, Z = 0.08) and (X = 0, Y = ±0.3, Z = 0.08m).

Fig 5. Time series variation of concentrations of two particle size fractions in the breathing zone with three different treatments applied.

A) without air cleaner, B) with room air cleaner and C) with TLA device. (Fraction 1 includes the particles between 0.3 and 0.5 μm. Fraction 2 includes the particles larger than 0.5 μm.)

Fig 6. Overall particle distribution over the entire measurement period with periodic movements.

Measuring interval: 23 s, i.e. 479 measurements for each particle size bin interval.

Fig 7. Variations of particle concentrations in the breathing zone when air cleaner (setting B) and TLA device (setting C) was used and duvet was lifted periodically.