Disinfecting with household bleach

Bleach is a cheap and widely available product usually sold as a liquid 5% concentrate solution for a range of household uses from general cleaning and sanitisation to purifying water in an emergency.

When diluting with water for disinfecting objects and surfaces it should be mixed in small batches for daily use as it deteriorates over time.

Clean items or areas to be disinfected before applying the appropriate solution which should be prepared in a well ventilated area.

For clarity I will list the volumes in standard measurements as well as the ratio because in an emergency you might not have a measuring jug available but with a simple cup and bucket can achieve the correct mixture.


High level:

Ratio 1: 10 household bleach to water, called "strong" chlorine water by CDC

• 50ml bleach, 450ml of water

For sanitising known contaminated areas such as blood and other bodily fluid spills and critical medical instruments and areas leave to soak for ten minutes, and to prepare larger quantities of 1: 100 solution.

Sometimes it may be sold in different concentrations so this graphic helpfully shows the most common and the different ratios you need to get the same solution.  

Intermediate level:

Ratio 1: 100 household bleach to water, called "mild" chlorine water by CDC

• 5ml bleach, 495ml of water

Use to sanitise PPE, clothing and hard surfaces, after ten minutes wipe away any residue with clean water and a cloth if necessary.

At this level it can be used to sanitise hands if you are then able to rinse with clean water afterwards as it is still caustic, or to prepare quantities of 1: 500 solution for food hygiene. 

Low level:

Ratio 1: 500 household bleach to water

• 5ml bleach, 2495ml of water

To ensure surfaces and utensils are safe to prepare food as normal household cleaning and for washing fruit and vegetables that are to be eaten raw.

Bleach is toxic and can chemically burn so take care to wear appropriate PPE when handling it and never mix with ammonia or acids as this will produce harmful gases, many people have accidentally poisoned themselves pouring bleach into toilets after using acidic cleaners releasing chlorine gas into confined spaces such as a toilet is not a good idea!

Whilst it is not recommended in an emergency you can even add unscented bleach to water that you have collected to sterilise it for drinking rather than boiling it, at the ratio 1:25000 4ml bleach to 100l of water stir and leave it for at least 30 minutes before drinking.

Take care

Roo

Coronavirus face masks

The COVID-19 coronavirus pandemic has caused panic buying worldwide and there is some misleading information

The US Surgeon General tweeted that face masks were ineffective but at the same time insisted that healthcare providers should have them, so do they work or don't they?

Obviously any protection is better than none but the level of protection varies dramatically depending on what mask you have

Surgical masks

These are designed to capture what people breathe out so they will limit the chance of the wearer from infecting others with what they expel but as they're so loose fitting and don't impede droplets they are next to useless as a means of personal protection

A scarf or bandanna would be similar the main benefit is these simple cloth face coverings keep your hands away from your face

Particulate respirators

These have several grades in Europe P1, P2 and P3 that corresponds to their ability to filter particles and liquids out of the air

America uses a slightly different system of 95, 99, and 100 prefaced with a letter to signify its resistance to oil N for not resistant, R for partially resistant and P for proof for strongly resistant

Some have one way exhale valves for easier breathing and the lettering isn't really important for the transmission of viruses but I will use P for comparison between the two systems as that is the highest rating 

P1 are standard dust masks able to block 80% of airborne particles only suitable for short term exposure in non hazardous environments such as doing some DIY at home

P2 are occupational standard filters that block 94% of particles, the US P95 offers slightly more protection blocking 95% and the P99 is a further step up at respectively 99%

P3 is the highest level of filter you can purchase blocking 99.95% and is equivalent to the US P100 with its ability to filter 99.97%

Both are considered to be effectively 100% for particles and droplets down to 0.3 of a micron

Mostly made as single use disposable masks that surround the nose and mouth but there are reusable versions where you simply replace the filters but retain the mask although this will require you to sterilise them safely

An N95 / P2 rated respirator is the recommended PPE (personal protective equipment) for blocking the SARS-CoV-2 virus but the higher the number the better it is obviously

There are some that include eye protection known as full face that prevent the virus being absorbed through contact with the eyes

So read the specification and know what you're buying, they do work so long as they're correctly fitted but your best defence is to isolate yourself as much as possible

Take care
Roo