Saturday 6 June 2020

Using a Fogger to disinfect the cottage?

Having seen the advice from the rental agency Sykes to use fogging, or ULV machines, to disinfect the holiday cottage I thought some investigation is in order before exposing our guests to these substances.  Here's one substance a local business is recommending as a biocide suitable to destroy Covid-19. It is called Vanoquat, it is used in animal husbandry and the food processing industry.   

Used as 1:25 dilution with water it is loaded into a fogging machine and you need about 3 litres of the solution in 100 Cubic metres. Our one bedroom cottage is about 75 Cu M, so we'd need around 2.5 litres sprayed around, as part of a two stage cleaning programme, so wash down surfaces first with detergent and water.  The instructions are lacking information about how soft furnishings should be treated, but you don't often get soft furnishings in cattle barns.

According to the local contractor, you then leave the treated area for at least 90 minutes. Again, there's no advice is the distributors safety documentation about how long should be left before human occupation in the area.

The chemical can cause permanent eye damage, it should not come into contact with the skin and the mist should not be inhaled. So the recommended PPE is waterproof boots, full body covering with waterproof suiting, rubber gloves on hands, eye and face protection. The safety sheet says no respiratory protection is required, but elsewhere advised not to breathe the mist, so I'm guessing a suitable respirator may be appropriate. Certainly all the videos I've seen, the fogger operatives are wearing respirators to protect against the mist.

If I was a guest in the cottage, I wouldn't want to sleep in that environment. There are some less toxic cleaning fluids, but they make no mention of application by fogging. In a Premier Inn customer assurance video they show their staff using a single stage (combined detergent/biocide) from hand spray bottles but only hard surfaces are treated.  The Covid-19 virus remains viable for a few days on soft surfaces.

We've chosen to use Ultraviolet lamps and superheated steam (using de-ionised water) to supplement a cleaning programme.

Here's the advice from the World Health Organisation:

In indoor spaces, routine application of disinfectants to environmental surfaces by spraying or fogging (also known as fumigation or misting) is not recommended for COVID19. One study has shown that spraying as a primary disinfection strategy is ineffective in removing contaminants outside of direct spray zones.

Moreover, spraying disinfectants can result in risks to the eyes, respiratory or skin
irritation and the resulting health effects.

Spraying or fogging of certain chemicals, such as formaldehyde, chlorine based agents or quaternary ammonium compounds, is not recommended due to adverse health effects on workers in facilities where these methods have been utilized.

Spraying environmental surfaces in both health-care and non-health care settings such as patient households with disinfectants may not be effective in removing organic material and may miss surfaces shielded by objects, folded fabrics or surfaces with intricate designs. If disinfectants are to be applied, this should be done with a cloth or wipe that has been soaked in disinfectant.

Other sources:

Edit: 26/06/2020

Some people are recommending the use of dilute Hypochlorous acid in foggers. A common way to manufacture this is by electrolysis of dilute salty water (Sodium Chloride) and indeed you can buy devices which make small quantities of dilute Hypochlorous acid.  The electrolysis produces Chlorine and Hydrogen; the Chlorine gas produced (in small quantities)  dissolves in water to form hypochlorous acid. Electrolysis of brine is the commercial process used to manufacture sodium hypochlorite bleach, i.e. the common household bleach.  It is known that breathing in bleach vapour damages the lungs. Common Bleach also contains sodium hydroxide, i.e. Caustic Soda arising from the electrolysis process.

The manufacturers of hypochlorous fogging machines that hypochlorous acid is produced naturally by the body as a defence against infection. No doubt it is, in minute quantities at a cellular level, but the body also produces quite a lot of hydrochloric acid in the stomach as part of the digestive process. In the wrong place in the body hydrochloric acid would do a lot of damage. Remember the burning pain of acid reflux in your throat?

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