Wednesday, May 6, 2020

The use of Heat for SARS-CoV-2 disinfection

There are four main methods to disinfect SARS-CoV-2 the virus that causes COVID-19.

  1. Time: The virus eventually no longer will be viable after a period of time. This depends on several things including the surface type, the temperature, and relative humidity. 
  2. Ultraviolet light (UV-C) also known as UVGI (Ultraviolet Germicidal Irradiation) at 254 nm works to alter the RNA of the SARS-CoV-2.
  3. Vaporized Hydrogen Peroxide 
  4. Temperature. Elevated temperatures reduce the viability of the virus.  


Decontamination of respirators was effective at 70 degrees Celsius for 60 minutes. These elevated temperatures may cause damage to respirator components.  

Stanford Medicine has done multiple studies decontaminating respirators with UV-C and heat. In there study they found repeated heating of masks with hot air at 75C for 20 cycles did not damage a respirator. An 8 W UVGI (254 nm) for 30 minutes for 10 cycles did not damage the respirator.

As I reviewed the 3M website masks appeared to have different temperature tolerances. 

Friday, May 1, 2020

Guidelines for Reopening Businesses and schools during COVID-19

The deeper you look the more you find - photo N. Carlson

Many places of employment are working through plans to reopen while minimizing transmission of SARS cov 2 the virus that causes COVID-19. The following is a list of guidances primarily from the CDC about opening businesses, schools and Universities. In the near future more specific information will become available, and this information will be added to the post. 

General guidance:

Back to Work Safely - AIHA offers industry specific guidance for getting back to work safely.

Business guide for responding to COVID-19 - CDC

Reopening Guidance for Schools and Businesses - CDC

How to clean and conduct risk management for COVID-19:

Cleaning and Disinfecting Tool - CDC

Disinfect Non-Emergency Vehicle with COVID-19 positive occupant - CDC

Reopening guidance for cleaning and disinfecting areas - CDC

Cleaning and Disinfecting Your Facility - CDC

Guidance for Schools for COVID-19  - CDC

Guidance for Higher Education Administration - CDC

Cleaning for CoVID -19 - Sustainable Mycology summary

LBC - General information on Deep Cleaning for Coronavirus - 3 min. 

Private Sector call on COVID-19 response from CDC 4/29/2020 -46 Min.

COVID-19 School response - March 26, 2020 - CDC - 61 min.

Saturday, April 25, 2020

CDC updates symptom list for COVID-19

Symptom Chart Provided by MNChildrens

The above chart helps individuals differentiate between the cold, flu, and COVID-19. The CDC has recently published and updated list of COVID-19 symptoms.  The list previously included the top three symptoms. The symptoms in Bold are new additions to the list.

  • Fever
  • Cough
  • Shortness of breath or difficulty breathing
  • Chills
  • Repeated shaking with chills
  • Muscle pain
  • Headache
  • Sore throat
  • New loss of taste or smell
The CDC has a Coronavirus Self-Checker to help people get a better idea if they have symptoms of COVID-19

Please see below about gastrointestinal symptoms and a recent NEJM publication noting a higher than normal incidents of stroke in younger coronavirus patients in New York City.

A doctor at the Mayo Clinic notes that patients can have gastrointestinal symptoms that are associated with COVID-19 with or without respiratory symptoms.  1 min. 

Washington Post summary of symptoms - 1 min. 

Dr. Justin Springer on the association between COVID-19 and increase incidence of stroke - 3 min. 

Tuesday, April 21, 2020

Cleaning for COVID-19

CDC guidance for cleaning and disinfecting facilities

There are several guidance documents on general cleaning guidelines for a COVID-19 area of concern.

Role of hand washing and surface cleaning - Click to enlarge graphic

MMWR reported on increased health concerns associated with use of cleaning chemicals.

The CDC has some good general guidelines.

CDC room clearance based on ventilation rates. How long do you have to wait before cleaning and putting another patient in the room?

CDC guidelines for household cleaning.

OSHA has some minimal guidance with references to the CDC. 

The US Army has a very good detailed protocol that may help answer specific questions about what is the proper order to clean an area.  

One minute summary of CDC's cleaning guidelines

How to disinfect home with COVID-19 patient - 2 min.

Portland State University deep cleaning high contact surfaces - 2 min.

Sunday, April 19, 2020

UV-C disinfection of hospital rooms

Electromagnetic spectrum - Stanford University
UV-C light in the range of 280 to 200 nm (254 nm the most effective) is a disinfectant used in laboratories and ventilation systems. Direct exposure to the light at this wavelength can severely damage skin and damage vision. UV light can also produce ozone, Ozone health effects are noted by the CDC.

The following links describe the use of UV-C lights for room disinfection.  One of the concerns is making sure that the light exposes all surfaces.  There are also concerns about the length of time needed.  The light does generate heat so no flammable objects can be close to the light. The UV-C light will decay in effectiveness over time. Specific meters are used in the UV-C light range to determine the level of exposure needed to kill the virus. Refer to the Wikipedia article on Ultraviolet Germicidal irradiation


CDC methods of disinfection  UVC kills bacteria and viruses more easily than bacterial spores.

Research Gate: inactivation of mold spores by UVC Aspergillus niger conidia are difficult to kill with UV-C light

Science Direct -Programmable and low cost UV-C room disinfection

NIH - Using UV-C light to disinfect high touch surfaces in hospitals.

Asian Journal - UVC kills bugs at home.

Indian J. of Med. and Biology - Surface disinfection by germicidal UV-C light

Dangers of UV-C light - 4 minutes

Applications of UV-C disinfection - BBC News - 2 min.

Duke Health: Benefits of room UV-C disinfection - 2 min.

Friday, April 17, 2020

MDH and CDC guidance for using paper bag to extend the life of N-95 respirators but not surgical masks

Paper bag with handles 8.5" x 6.5" x 3.5"  Name and date are clearly marked on the bag

Respirator straps are hung from paper bag handles

The respirator is suspended above the bottom of the bag

A 2 gram desiccant pack is placed at the bottom of the bag to absorb moisture from the mask to slow down bacterial and fungal growth. The amount of desiccant needed may vary dependent on storage conditions.

Please see the disposable respirator post for links to the Minnesota Department of Health and the CDC for the number of times these respirators can be used. Guidance on the number of uses will vary by health care provider. The length of storage time will vary from 5 to 7 days. This is based on the anticipated COVID-19 survival time on surfaces.

Experience from nurses indicate that moisture in the masks is an issue. The straps also tend to wear out after repeated use.

To reduce particle loading on the mask, staff are asked to refrain from wearing make-up in areas that will contact the surface of the mask.

Surgical Masks:  Surgical masks provide some protection from droplets but they are primarily designed to protect the patient from the provider because the mask does not provide a tight face seal. Never reuse, wash or disinfect surgical masks. Please see Delaware Health and Social Services Division of Public Health - Proper use of surgical masks

Sunday, April 12, 2020

How long do Coronaviruses Live on Surfaces

According to an April 2, 2020 Medscape article on coronaviruses on fabrics researcher still need to study how the virus survives on clothing. The CDC recommends washing clothes on the warmest possible setting and drying the clothes thoroughly. Please review CDC's home cleaning recommendations for a suspected or known COV-19 person in the house. 

There are worse jobs than cleaning up a space for COVID-19. The video below from National Geography shows extreme cleaners in action.  Not recommended for viewing by those that are easily nauseated. 

Extreme Cleaning - National Geographic - 3 min. 

Thursday, April 9, 2020

UV-C light disinfection of n-95 face masks

In an effort to prolong the life of N-95 face masks, many institutions have been using UV-C light disinfection.  It is being looked at by 3M but they have not completed testing. This method has not yet received FDA approval.

Here are some safety notes to note up front.  UV-C light is hazardous.  Do not expose skin or look at the light as it will cause damage. The light must be turned on remotely without individuals present in the room. The lamps can get hot, and ozone may be produced.

There are concerns with making sure all parts of the mask are disinfected. There are also concerns that the UV-C light will cause the material to photo degrade and loose its effectiveness.

Not all UV lights are equivalent (notes from Nancy Rolstad and Wikipedia UV)
  • UV-A lights (the ones used in a tanning bed) do not have sufficient germicidal properties (long-wave UV) It is associated with skin aging
  • UV-B light is a shorter wavelength of light associated with skin burning.
  • UV-C lights are necessary for disinfection. (aka UVGI germicidal irradiation or shortwave UV)
  • UV-C light bulbs efficiency is reduced over time. A UV meter is necessary to measure the quality of the light source. 
  • UV-C light is absorbed by the ozone layer and the atmosphere. That is why the sunlight that reaches the earth does not have good disinfecting properties for COVID-19.
J. of 

The University of Nebraska has excellent guidance on the use of UV-C light for COVID-19 disinfection including information on a COVID-19 UV-C decontamination process They also looked at using the UV-C lights in biological safety cabinets to disinfect masks.  The University of Nebraska produced specific information on UV-C light respirator decontamination. 

Stanford University also has a UV-C COVID-19 disinfection process.

In Science Daily: Researchers report a 99.9% reduction in surface COVID-19 levels with a 30 second dose of UV-C light.  The dose was not specified.

U of M's CIDRAP has weighed in on N-95 reuse. Current methods are for an emergency use only to extend the amount of stock available. The UV-C light does begin degrading the material. Under the emergency circumstances they recommend 5 cycles at 1 J/cm2 per cycle.

Conversion of milliwatts/cm^2 to Joules/cm^2 Milliwatts to Joules converter


Applied Environmental Microbiology - This was a study on the use of biological indicator strips to verify sterilization with plasma, UV-C, and blue light.

NIH publication on UV-C disinfection for COVID-19

American Medical Association - Tackling the shortage of N-95 respirators with Novel Decontamination.

Omaha hospital using ultraviolet light (UV-C) to disinfect masks - 3:32 min. 

Duke Health - Benefits of UV-C disinfection of patient rooms  - 2:17 min. 

DIY disinfection of masks with 30W UV-C light (Not FDA approved) 11 min.
I am working with a health physicist to verify the calculations. 

Sunday, April 5, 2020


Check out the NIH DIY 3D printer COVID-19 page for some original solutions to PPE problems.

Cloth face masks:

Allina health has looped face masks that they are accepting for donations.

There is an upgraded DIY mask from Allina Health with a built in pipe cleaner to improve the fit of the mask around the nose.   I will give it a try.  I could not locate 1/4 inch elastic bands because all stores were sold out.  I will try with larger elastic bands and see how it goes.

Face shields

St. Cloud State converted plastic overhead projector sheets into face shields.

I will be adding to this page in subsequent days.

A DIY video from Blue Cross/Allina on making the looped face mask - 19 minutes