A NIH study showed how a face mask may serve as a humidifier.

****!!!!**** "This cold mist humidifier for the bedroom features an innovative electrolytic sterilization module to ensure a healthy indoor environment. Using just tap water, this humidifier runs the water through the electrolytic process to create slightly acidic electrolized water, which is a strong and natural disinfectant. Meanwhile, the humidifer's ultrasonic atomizer ensures that the electrolyzed water is converted into a hydroxyl mist, which removes odors, oxidizes contaminants, and kills viruses and bacteria. Independent testing has shown that this dry air humidifier consistently had an airborne bacteria kill rate of 99.9% in two hours."

"Such interventions with humidifiers have been realized since the 1960s with promising results (122–127). More recently, a study in Minnesota found that humidifying preschool classrooms during January to March to ∼45% RH results in a significant reduction in the total number of influenza virus and viral genome copies found in the air and on objects compared to control classrooms"

****!!!!**** Dry rooms and air-conditioned indoor spaces hike Covid-viral infection, conclude Indian and German researchers in their meta-study. They're urging optimum humidity standards for building interiors and public transport.

heightened coronavirus contagion risks in dry, indoor conditions during the winter months.

****!!!!**** {Note: These conclusions were based on theoretical modeling, not experimentation.} "A ventilation rate of 0.5 ACH, the change of RH between 20% and 53% was predicted to have a small effect on the infection risk, while at a ventilation rate of 6 ACH this change had nearly no effect. On the contrary, increasing the ventilation rate from 0.5 ACH to 6 ACH was predicted to decrease the infection risk by half which is remarkably larger effect compared with that predicted for RH. It is thus concluded that increasing the ventilation rate is more beneficial for reducing the airborne levels of SARS-CoV-2 than changing indoor RH."

Mounting evidence from scientific community seems to suggest that COVID-19 virus can potentially spread by airborne transmission. As a result, methods and techniques for preventing environmental contagious, such as ventilation or air filtration have been ...

"Exposure of mice to low humidity conditions rendered them more susceptible to influenza disease. Mice housed in dry air had impaired mucociliary clearance, innate antiviral defense, and tissue repair function. Moreover, mice exposed to dry air were more susceptible to disease mediated by inflammasome caspases. Our study provides mechanistic insights for the seasonality of the influenza virus epidemics, whereby inhalation of dry air compromises the host’s ability to restrict influenza virus infection."

"Humidifiers had a modest effect on room humidity, but became contaminated over time despite the use of sterile water. Contamination with potential pathogens spread in vapor may pose a risk to immunosuppressed patients, particularly during the summer. This risk is only partially mitigated by replacing humidifiers after three days. "

"With prehumidification, recovery rates (± standard deviations) were much higher for nonenveloped viruses (T7 coliphage, 28% ± 19% with prehumidification versus 0.02% ± 0.01% without prehumidification; poliovirus, 29% ± 5% versus 3.2% ± 1.8%) but were unchanged for enveloped viruses (Semliki Forest virus [SFV], 32% ± 7% versus 42% ± 8%; Langat virus, 42% ± 10% versus 51% ± 12%) Benbough attributed the inactivation of nonenveloped viruses to structural rearrangement during abrupt rehydration in the impinger collection medium and suggested that slower rehydration rates, such as those experienced during the prehumidification process, were more favorable for polioviruses and coliphages" "Viruses that partition on the surface of aerosols may be subject to damage due to surface tension, shear stress, and conformational rearrangement driven by hydrophobicity." "Results showed that enveloped viruses lost infectivity dramatically (up to four orders of magnitude) due to aeration, while the nonenveloped ones did not." "Higher RH allows for larger final aerosol size and larger surface area due to less evaporation and, thus, greater potential for surface inactivation of hydrophobic lipid-containing viruses (i.e., enveloped viruses). Nonenveloped viruses are less likely to be affected." "While salts appear to be toxic to enveloped viruses, addition of salts to the medium has been shown to improve rather than reduce the viability of nonenveloped viruses... Benbough (1) suggested that salts can slow the rehydration process ... and thus reduce the chance of structural rearrangements that can be damaging in the capsid of nonenveloped viruses. Our interpretation of the enhanced viability is that salts can keep the aerosol and the virus in it from drying out completely at RHs above the ERH and thus reduce the chance of unwanted structural rearrangements during rehydration. This effect would benefit the nonenveloped viruses that need to retain their structural water; meanwhile, they are not susceptible to damage by salts, as are enveloped viruses."

[**Side thought: Contaminated or high-mineral (or high turbidity) local may be detrimental even in spray bottles!!} The U.S. Department of Energy's Office of Scientific and Technical Information

Testing is needed beyond just for minimum approval, and needs to be application-type specific.

Only if you clean them often—we’re talking daily—can you breathe easy.

This article aims to draw the attention of the scientific community towards the elevated risks of airborne transmission of diseases and the associated risks of epidemics or pandemics. The complexity of the problem and the need for multidisciplinary research ...

This article aims to draw the attention of the scientific community towards the elevated risks of airborne transmission of diseases and the associated risks of epidemics or pandemics. The complexity of the problem and the need for multidisciplinary research ...

CDC - Indoor Environmental Quality - NIOSH Workplace Safety and Health Topic

HVAC strategies with potential to reduce the risks of infectious aerosol dissemination: air distribution patterns, differential room pressurization, personalized ventilation, source capture ventilation, filtration (central or local),and controlling temperature and relative humidity. [Doc includes Ventilation requirements for Healthcare, & general areas. Concerns about healthiness of outdoor air. Etc] American Society of Heating, Refrigerating and Air-Conditioning Engineers

Includes humidifiers, but not CD

Comprehensive, user-friendly humidity calculator supporting all popular parameters including dew/frost-point, %rh, ppmV, moisture content and more.

A calculator that can calculate the relative humidity based on temperature and water content

{Wide variety of methods}This article aims to draw the attention of the scientific community towards the elevated risks of airborne transmission of diseases and the associated risks of epidemics or pandemics. The complexity of the problem and the need for multidisciplinary research ...

The review shows that ventilation has various positive impacts on health and productivity of building occupants. Ventilation reduces the prevalence of airborne infectious diseases and thus the number of sick leave days. In office environment a ventilation rate up to 20-25 L/s per person seem to decr …

{Mechanics of humidity and temperature changes.} Dear Tom, What is the best humidity range to have in the home over the winter? Mike Michalides Elgin Dear Mike, A good rule of thumb is to keep the indoor relative humidity in winter at about half …

Safety and Health Topics | Indoor Air Quality - Frequently Asked Questions