scholarly journals Bacteriological aspects of air-conditioning plants

1968 ◽  
Vol 66 (4) ◽  
pp. 567-584 ◽  
Author(s):  
W. Whyte
Keyword(s):  
Air Conditioning ◽  
Ventilation System ◽  
Free Water ◽  
Filtration Efficiency ◽  
Bacterial Concentration ◽  
Critical Areas ◽  
Critical Zones ◽  
Micro Organisms ◽  
Number Of Bacteria ◽  
Fair Degree

An investigation was carried out into the bacteriological performance of three air-conditioning plants in a hospital ward. Two of these plants had the facility for recirculating part of the ward air.An equation has been derived comparing the concentration of bacteria which would be expected to be given off by the humidifiers in the ventilation system, with the concentration of bacteria in the recirculatory tank. The bacterial particles given off by these humidifiers were of nuclei droplet size, and were found to penetrate the filters used with a fair degree of ease. Although the number of bacteria in the humidifier water remained insignificant with a constant overflow of water into the recirculatory tank, on one occasion a build-up of bacteria was demonstrated when the overflow ceased. For hospital use humidifiers of a non-recirculatory type should be used.The concentration of bacteria on the surface of the recirculatory ducts was assessed, as also were those on the surface of the supply ducts under full fresh air and recirculation. The concentration of bacteria in the supply ducts was low and the use of terminal filters was not merited, although care should be taken to prevent the build-up of bacteria in inlet grills and diffusers. The bacterial concentration in the exhaust ducts was found to be quite high. It was therefore thought that in critical areas, where the ventilation plant may be shut off, the use of some device to prevent reversed air flow may be necessary.The count of various types of micro-organisms in the fresh air and two-thirds recirculated air are given along with their size distribution. The results of the effect of filtration on the concentration of bacterial particles throughout the air-conditioning plant is given under full fresh air and recirculation. These concentrations appear quite satisfactory. It was found that one set of filters had been overgrown by mould because of free water being brought over from the humidifier. Measures have been suggested to overcome this. When primary or prefinal filtration was approximately 90% efficient to Aloxite 50 (B.S. 2831 Test Dust no. 2) it was demonstrated that a fair approximation to the final filtration figure could be obtained by reference to the quoted efficiency of the final filter to Aloxite 50. After similar primary filtration it was demonstrated that the final filtration of filters against recirculated and fresh air was approximately the same. Owing to the higher number ofStaph. aureusin recirculated air, higher efficiency filtration may be required.Standards of filtration efficiency for critical and non-critical zones are suggested.

Investigation and Research of Biological Contamination of HVAC in Public Places

2011 ◽  
Vol 250-253 ◽  
pp. 2719-2722
Author(s):  
Xin Li ◽  
Ya Wei ◽  
Liang Li
Keyword(s):  
Public Health ◽  
Air Conditioning ◽  
Ventilation System ◽  
Cooling Water ◽  
Public Places ◽  
Biological Contamination ◽  
Central Air Conditioning ◽  
Normal Method ◽  
Number Of Bacteria ◽  
Public Health Standard

According to the normal method for sampling in the appendix of “The Central Air-Conditioning Ventilation System of Public Health Standard” by the ministry of health in 2006 were the HVAC on-site examined and sampled. The examined indicators include: total number of bacteria, fungus and beta Streptococcus in air supplied outlet, Legion Ella pneumophila in cooling water, the quantity of dust and microbe amounts to each square meter pipeline surface area and other sanitation indexes.

scholarly journals Dynamics of infection of the blood stream and internal organs of white mice withSalmonella typhiby intraperitoneal injection

1962 ◽  
Vol 60 (3) ◽  
pp. 311-321 ◽  
Author(s):  
B. Gerichter ◽  
D. L. Boros
Keyword(s):  
Blood Count ◽  
Gradual Increase ◽  
Bacterial Count ◽  
Blood Stream ◽  
Gradual Decrease ◽  
Bacterial Concentration ◽  
Internal Organs ◽  
Micro Organisms ◽  
Number Of Bacteria ◽  
Second Peak

An LD 50 doseS. typhi(strain Ty was injected intraperitoneally into white mice, and the number of micro-organisms was determined after 1 min. and subsequently, in the blood, and after 3 hr. and subsequently, in the spleen and liver. The course of the infection was observed for 34 days.The number of bacteria gradually increased in the blood stream during the first post-infective hours. It was possible to differentiate by external signs from the sixth post-infective hour and onwards between sick animals and recovering ones. This difference corresponded to the bacterial concentration in the blood stream and internal organs.In the sick animals the increase in the bacterial count of blood stream continued till 9–10 hr. after the inoculation, when it reached its first peak. During the following 8 hr. a clear decrease in the blood count was evident which was attributed to the ‘clearing mechanism’ of the blood. The onset of a new bacterial rise in the blood stream appeared 18 hr. after the inoculation and reached a second peak during the further 6–8 hr.In contrast to the observed decrease in the bacterial blood count, a steady and gradual increase in the count of the internal organs was seen; it was steadily progressive till the exitus.In the recovering animals a steady decrease in the bacterial blood count was recorded. Between 24 and 26 hr. the number of micro-organisms in the blood and spleen was found to be 400 times less in the recovering animals than in the moribund ones. From 48 hr. and onwards a slow and gradual decrease in the bacterial count of the surviving animals was observed. The blood became sterile after 25 days. In the spleen and liver of the surviving animals after 48 hr. a new increase in the bacterial count is evident, accompanied by hyperplasia of the spleen. The number of bacteria reached a new peak in the liver on the third day and in the spleen on the fourth day after the infection.Subsequently a slow and gradual decrease in the bacterial count was observed in both organs, but even after 34 days a small number of persisting bacteria in the spleen and liver tissue may be found.

scholarly journals Verification of the effect of sleeping environment and humidification on middle-aged people in whole-house air-conditioning ventilation system housing

2019 ◽  
Vol 111 ◽  
pp. 02044
Author(s):  
Akemi Iwaki ◽  
Takashi Akimoto ◽  
Naho Misumi ◽  
Takuya Furuhashi
Keyword(s):  
Blood Pressure ◽  
Moisture Content ◽  
Air Conditioning ◽  
Sleep Latency ◽  
Ventilation System ◽  
Circulation Type ◽  
Living Environment ◽  
Aged People ◽  
Air Circulation ◽  
Skin Moisture

This study focused on the thermal comfort of air circulation-type whole-house air-conditioning ventilation systems. We studied the influence of 24-h continuous whole-house air-conditioning on the living environment in which the occupant is sleeping. A survey was conducted in the summer of 2016 and winter of 2017 to ascertain the influence on the sleeping environment, skin moisture content, and blood pressure. We then compared the results with those of the sleeping environment of residents in air-conditioned housing surveyed the previous year. The sleeping environment when using a personal humidifier around the occupant’s head was examined during winter when the humidity is low. The results indicated that sleep latency was significantly shortened in the 24-h continuous whole-house air-conditioning ventilation system in both summer and winter because the temperature control of the bedroom before going to bed affects the sleep latency. Subjectively, no participants felt dryer than the values measured in the bedroom environment. The results implied that the comfort of the entire building was improved with continuous air-conditioned housing.

Airborne bacteria concentrations and related factors at university laboratories, hospital diagnostic laboratories and a biowaste site

2011 ◽  
Vol 64 (3) ◽  
pp. 261-264 ◽  
Author(s):  
Sung Ho Hwang ◽  
Dong Uk Park ◽  
Kwon Chul Ha ◽  
Hyun Woo Cho ◽  
Chung Sik Yoon
Keyword(s):  
Sampling Site ◽  
Ventilation System ◽  
Airborne Bacteria ◽  
Gram Negative Bacteria ◽  
Indoor Environments ◽  
Related Factors ◽  
P Values ◽  
Regular Control ◽  
Number Of Bacteria

AimsTo evaluate concentrations of airborne bacteria in university laboratories, hospital diagnostic laboratories, and a biowaste site in Seoul, Korea. To measure total airborne bacteria (TAB), the authors assessed sampling site, type of ventilation system, weather and detection of Gram-negative bacteria (GNB), indoors and outdoors.MethodAn Andersen one-stage sampler (Quick Take 30; SKC Inc) was used to sample air at a flow rate of 28.3 l/min for 5 min on nutrient medium in Petri dishes located on the impactor. A total of 236 samples (TAB, 109 indoor and nine outdoor; GNB, 109 indoor and nine outdoor) were collected three times in each spot from the 11 facilities to compare airborne bacteria concentrations.ResultsTAB concentrations ranged from undetectable to 3451 CFU/m3 (mean 384 CFU/m3), and GNB concentrations from undetectable to 394 CFU/m3 (mean 17 CFU/m3). TAB concentrations were high in window-ventilated facilities and facilities in which GNB were detected; concentrations were also high when it was rainy (all p values <0.05). TAB concentrations correlated significantly with GNB (r=0.548, p<0.01), number of bacteria species (r=0.351, p<0.01) and temperature (r=0.297, p<0.01). The presence of heating, ventilating, and air conditioning (HVAC), the number of TAB species and the detection of GNB affect TAB concentrations in laboratories.ConclusionsIt is recommended that special attention be given to regular control of indoor environments to improve the air quality of university and hospital laboratories.

scholarly journals Performance of oil-free water-cooled chiller for a shopping center air conditioning system

2021 ◽  
Vol 673 (1) ◽  
pp. 012010
Author(s):  
A Yatim ◽  
J A Prima ◽  
M A Jofansya ◽  
M I Alhamid ◽  
Budihardjo ◽  
...  
Keyword(s):  
Air Conditioning ◽  
Free Water ◽  
Shopping Center ◽  
Air Conditioning System

scholarly journals Study on IBS Cooling Panel Wall System with Difference Types of Cooling Mediums

2020 ◽  
Vol 11 (2) ◽  
Author(s):  
Eny Nor Syahira Mohamad Hashim ◽  
◽  
Norhafizah Salleh ◽  
Noor Azlina Abdul Hamid ◽  
◽  
...  
Keyword(s):  
Relative Humidity ◽  
Air Conditioning ◽  
Ventilation System ◽  
Target Strength ◽  
Outdoor Temperature ◽  
Design Concepts ◽  
Building Ventilation ◽  
American Society ◽  
Wall System ◽  
Indoor And Outdoor

This paper proposes a cooling house system that can promote thermal comfort in buildings without air-conditioning. The cooling panel wall forms a part of an Integrated Building System (IBS), and is essentially made of tubes filled with either water or glycerin as the coolant. Target strength for the panel wall was designed based on the Malaysian Standard (MS) while the building ventilation system followed the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) standard. The results are reported based on indoor and outdoor temperature difference together with relative humidity to identify the best performing house model and also coolant. The outcome of this research is expected to add value to design concepts with a better promotion of air flow and circulation in the building, without over-usage of natural resources and higher building cost to achieve the same objective.

Simulation of COVID-19 indoor emissions from coughing and breathing with air conditioning and mask protection effects

2021 ◽  
pp. 1420326X2110395 ◽  
Author(s):  
Carlo Cravero ◽  
Davide Marsano
Keyword(s):  
Air Conditioning ◽  
Vaccination Campaign ◽  
Ventilation System ◽  
Management Strategies ◽  
Air Conditioning System ◽  
Beneficial Effects ◽  
Mass Vaccination Campaign ◽  
Future Events ◽  
System Configurations ◽  
Different Characteristics

The COVID-19 infection has emerged as a disruptive pandemic at worldwide level. The study of the mechanism of contagion is one of the greatest challenges before a mass vaccination campaign that would protect populations. The study can support the development of knowledge and tools to develop possible strategies for containing its spread in future events. The saliva droplet aerosol expelled during breathing or coughing is the main cause for the propagation of the SARS-Cov-2. In this work, a URANS CFD approach was used to simulate the dispersion from the mouth of these particles in closed environments. The air conditioning system was considered. The conditions were varied to determine their impact on the diffusion of the aerosol. Lagrangian and Eulerian numerical approaches were used to model the coughing and the breathing events. These were validated with the puff theory, numerical and experimental results. A realistic case of a meeting room with two persons was simulated. Different characteristics of the expulsed aerosols and different ventilation system configurations were considered to demonstrate how these simulations can support management strategies for indoor occupation. Finally, the effect of the protective mask was introduced to quantify its beneficial effects to support safe indoor occupation.

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