Aerosolization of Aspergillus niger spores from colonies on different positions of a circular tube

Xian Li,Shugang Wang,Tengfei Zhang,S.I Tanabe,J Kurnitski,L Mazzarela,M.C Gameiro Da Silva,H Zhang,G Cao,I Nastase,C Inard,P Wargocki

doi:10.1051/e3sconf/201911102030

Abstract

Subject to the blowing air, fungal spores can be aerosolized from the colonies growing on cooling coils. The blowing air may accelerate and decelerate when passing a coil. The caused spore detachment may be different, when the fungal colonies grow on different positions of the coil. This study investigated the aerosolization of Aspergillus niger spores from a colony on a circular tube in a wind tunnel. The colony was first cultured in the carved groove along the longitudinal tube, and then the spores were aerosolized by a gradual increase of the blowing air speed. The grown colony on four different positions of the coil surface were blown for aerosolization. In addition, the airflow surrounding the circular tube was numerically solved to estimate the drag force for aerosolization of the spores. The results revealed that the collected airborne spores when the colonies were located tangentially to the upcoming airflow were six to eight times of those when the colonies were located parallel with the upcoming airflow for both the 4-day-old and 10-day-old colonies. The local air speeds in different positions of the tube were highly different from the inlet air speed of the wind tunnel. Such difference should be accounted for when estimating the drag force to aerosolize the fungal spores on the coils.

Highlights

Fungi in heating, ventilating, and air conditioning (HVAC) systems have caused increasing concern [1, 2]
This study investigated the aerosolization of A. niger spores from a colony growing in different positions on a circular tube in a wind tunnel
The results revealed that the drag forces required to aerosolize spores from the two growth ages’ colonies were in accordance with the ranges of the detachment forces measured by the atomic https://doi.org/10.1051/e3sconf/201911102030 force microscope (AFM)

Summary

Introduction

Fungi in heating, ventilating, and air conditioning (HVAC) systems have caused increasing concern [1, 2] Fungal spores and their metabolic byproducts contribute to inflammation, infection and asthma for occupants [3,4,5]. The growing spores can be aerosolized from the coil surface, if the aerodynamic forces exceed the binding forces of fungal spores with their colonies [13, 14]. Because of the difference of the air speed in different positions on the coil, the exerted aerodynamic forces to the growing fungal spores in different positions are different. This study investigated the aerosolization of A. niger spores from a colony growing in different positions on a circular tube in a wind tunnel. Numerical simulation of the airflow surrounding the circular tube was performed to estimate the drag force by the sweeping air for aerosolization of the fungal spores

Materials and methods

Numerical simulation of airflow surrounding to the circular tube

Results

Conclusions