If you have Long Covid it makes sense to avoid re-infection, especially as research is showing that multiple COVID-19 infections cause cumulative damage. Aside from masking, one way to reduce the risk of infection is through checking air quality with carbon dioxide (CO2) monitors (see 2021 research here).

We exhale C02 when we breathe out. And, since Covid is airborne, a higher level of CO2 can mean a higher accumulation of airborne virus in the air. So checking the air quality is a handy way of making decisions about which indoor spaces are safer than others.

CO2 monitors measure the amount of carbon dioxide in parts-per-million. Lower levels of CO2 mean more fresh air is available and there’s likely to be less risk of Covid. Less than 800ppm is relatively safe. Over 1000 is bad.

This article from ABC News gives a good summary of CO2 monitoring. It includes this info:

Professor Morawska says the best CO2 meters are those that use technology called Non-Dispersive Infra-Red (NDIR) detectors. These measure the absorption of infrared light by CO2.

There are air monitoring experts like Jeffrey Siegel, a professor of civil engineering at the University of Toronto, who says you need to be careful using CO2 monitors.

He says they need to be calibrated properly and factors like water vapour in the air can give false measurements.

Professor Siegel also argues it’s important to measure CO2 levels over time, and to understand that different parts of the room will give different measurements.

“CO2 monitoring is fine if it’s done well,” he says.

Otherwise, he says money is better spent on improving ventilation and air filtration.

– “Portable CO2 meters could be used to help fight coronavirus transmission, experts say”. ABC News, 11 September 2021

Here’s Australian expert group OzSage’s page on CO2 monitoring and ventilation.

I recommend you read Violet Blue’s review of the Vitalight and the Aranet4. I only know about the existence of these monitors because of Violet and her amazing ongoing research into Covid prevention. Violet recommends the Vitalight Mini (pictured below).

Here’s a video review of low cost (under $100 C02 meters).

A Few CO2 Monitors To Consider

The Vitalight Mini is a cheap CO2 monitor that has good accuracy, though you need to make sure you calibrate it outside in fresh air before using. The monitor gauges air quality quickly and gives an indication of safety with a colour-coded display. An alarm goes off if CO2 is over 1000ppm. Is very compact and can be worn around the neck. Has a USB rechargable battery. US based so may require an adapter or converter. One of the cheapest CO2 monitors you can buy so worth looking at.

The Aranet 4 is a high-end air quality monitor. It offers colour-coded readings, letting you know when the air quality deterioates. It’s battery-operated, wireless and connects to an app which looks at data from the last 7 days. The monitor is US-based and not available in all countries. It’s not cheap so not ideal if you’re on a budget.

The Vision CO2 Monitor is a UK manufactured high-end monitor with a colour-coded screen that goes yellow, orange and red as the air quality progressively worsens. It’s USB-powered so needs to be constantly plugged in and it’s designed to be mounted on the wall. It uses an NDIR sensor and comes with a configurable app. Not cheap but looks like good quality.

The AirCO2ntroller has an unpronounceable name but it has British-made sensors and is small and portable. It gives PPM readings plus temperature and humidity data. Measures in real time every second and can give an alert is air quality deteriorates. Runs on batteries. Mid range pricing though you may get a deal as the site seems to offer sales regularly.

The Inkbird C02 Monitor is another budget option. It’s 90x90x40mm so it’s semi-portable but is designed to be wall-mounted. Offers temperature and humidity readings as well as CO2. It’s Wi-fi capable and links to an app with historical data and export functions. It gives an alert at a preset value.

You’ll find a number of cheaper CO2 monitors on Amazon. As with the devices listed above, I don’t vouch for their quality. As mentioned, check out Violet’s review for more detail on the Aranet and Vitalight.