Method for Comparing Concentrations of the Open-Air Factor

Cox, C. S.; Hood, A. M.; Baxter, Jean

doi:10.1128/aem.26.4.640-642.1973

Cited by 16 publications

(6 citation statements)

References 2 publications

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“…Factors affecting the viability of a virus during nebulization include nebulizer type, nebulizer air pressure, nebulization time, microorganism type, and humidity of the dilution air (Adams et al 1982;Sattar and Ijaz 1987). Marthi (1994) listed humidity, temperature, radiation, and open-air factors (Cox et al 1973) as the most important parameters influencing the viability of airborne microorganisms. The method of aerosol generation, composition of the generation fluid, sampling method, and collection medium were deemed to be secondary parameters.…”

mentioning

confidence: 99%

Effects of humidity and other factors on the generation and sampling of a coronavirus aerosol

et al. 2007

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Suspensions of transmissible gastroenteritis virus (TGEV), a porcine coronavirus, were nebulized at rates of 0.1-0.2 ml/min into moving air using a Collison nebulizer or a plastic medical nebulizer operating at pressures ranging from 7 to 15 psi. The airborne viruses were collected on heating, ventilating, and air conditioning (HVAC) filters in an experimental apparatus and also sampled upstream of these test filters using AGI-30 and BioSampler impinger samplers. To study the effects of relative humidity (RH) on TGEV collection by the filters and samplers, the virus was nebulized into air at 30, 50, 70, and 90% RH. There were no significant changes in virus titer in the nebulizer suspension before and after nebulization for either nebulizer at any of the pressures utilized. Aerosolization efficiency -the ratio of viable virus sampled with impingers to the quantity of viable virus nebulizeddecreased with increasing humidity. BioSamplers detected more airborne virus than AGI-30 samplers at all RH levels. This difference was statistically significant at 30 and 50% RH. Nebulizer type and pressure did not significantly affect the viability of the airborne virus. Virus recovery from test filters relative to the concentration of virus in the nebulizer suspension was less than 10%. The most and the least virus were recovered from filter media at 30% and 90% RH, respectively. The results suggest that TGEV, and perhaps other coronaviruses, remain viable longer in an airborne state and are sampled more effectively at low RH than at high humidity.

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Effects of humidity and other factors on the generation and sampling of a coronavirus aerosol

et al. 2007

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“…Analogous distributions are thought to occur for other causes of viability loss, e.g., oxygen and the open air factor (15,17,21).…”

Section: Appendixmentioning

confidence: 89%

Inactivation kinetics of some microorganisms subjected to a variety of stresses

Cox¹

1976

Appl Environ Microbiol

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Loss of viability in aerosols of Escherichia coli B, E. coli commune, E. coli Jepp (in nitrogen atmospheres), and Semliki forest virus (in air) was determined as a function of relative humidity at 26.5 C. The decay patterns could be accounted for accurately by means of an equation derived from a postulated mechanism involving population distributions and first-order denaturation kinetics. Analyses of published curves describing loss of viability (all of which were semiexponential, ie., J-shaped) for various microorganisms stressed by different techniques showed that the proposed mechanism also provided an explanation for effects of the following factors (in the absence of open air, oxygen, or radiation): (i) influence of relative humidity upon aerosol survival; (ii) dissemination of aerosols from the wet and dry states; (iii) protecting additives; (iv) relative humidity change before reconstitution; (v) reconstituting fluids; (vi) water content of freeze-dried product; (vii) storage gas; and (viii) storage temperature. The data indicate that low temperatures and high pressures were likely to be conducive to the preservation of viable bacteria and viruses, provided that cold shock and decompression shock were absent.

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“…111 The system produces hydroxyl radicals from a reaction of ozone and water vapour catalysed by an olefin (D-limonene). 112 Hydroxyl radicals may be present in open air, with the main source of hydroxyl being the photolysis of ozone e this could relate to the 'open air factor'. Hydroxyl radicals have been shown to possess disinfection characteristics.…”

Section: Preventing Infection Through Ventilationmentioning

confidence: 99%

Roles of sunlight and natural ventilation for controlling infection: historical and current perspectives

Hobday¹,

Dancer

2013

Journal of Hospital Infection

142

119

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Current knowledge of indoor transmission of pathogens is inadequate, partly due to lack of agreed definitions for particle types and mechanisms of spread. There is recent evidence to support historical data on the effects of natural ventilation but virtually none for sunlight. Modern practice of designing healthcare buildings for comfort favours pathogen persistence. As the number of effective antimicrobial agents declines, further work is required to clarify absolute risks from airborne pathogens along with any potential benefits from additional fresh air and sunlight.

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Method for Comparing Concentrations of the Open-Air Factor

Abstract: It is shown how concentrations of the open-air factor may be compared from day to day; this has not been possible previously.

Cited by 16 publications

References 2 publications

Effects of humidity and other factors on the generation and sampling of a coronavirus aerosol

Effects of humidity and other factors on the generation and sampling of a coronavirus aerosol

Inactivation kinetics of some microorganisms subjected to a variety of stresses

Roles of sunlight and natural ventilation for controlling infection: historical and current perspectives

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