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This under-$20 device repels mosquitoes without sprays, candles or flames

This under-$20 device repels mosquitoes without sprays, candles or flames
Posted at 7:30 AM, May 16, 2022

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The sounds of summer: Music bumping from passing cars, the smack of a baseball bat against a ball, kids playing at sunset — and the high-pitched whine of a hungry mosquito circling your head.

That last one isn’t just annoying, of course. Mosquito bites are painfully itchy and can spread viruses like West Nile and  Zika. In certain climates, mosquito repellent is a must for any outdoor activity.

If you find yourself getting doused in bug spray and firing up citronella candles just to enjoy an evening on the porch, check out the Thermacell Patio Shield — it’s a mosquito-repelling device that’s scent-free, smokeless and it’s on sale now at Amazon.


The Patio Shield is what’s called an “emanator,” a device that permeates the air around it with an insect repellent. It works by heating a small mat coated in insect repellent — in this case, metofluthrin — which disperses the chemical into the surroundings.

A 2007 study of such devices showed that they can be highly effective and a 2021 study of passive metofluthrin dispensers found they had a significant impact on mosquito activity. In the earlier study, researchers donned Tyvek protective gear and counted how many mosquitos landed on them before and after deploying an emanator. They tested it out in two different (very humid) locations, Florida and Washington state.

In Florida, they found the emanators decreased mosquito counts by up to 95%. In Washington, it was 97%.


Thermacell’s Patio Shield is meant to provide protection within a 15-foot radius. It’s more of a relaxing-on-the-patio product than bug sprays, which allow you to be more active, since the protection from the barrier doesn’t travel if you move outside its radius.

What Do the Reviews Say?

With more than 41,000 ratings, the Patio Shield has an average rating of 4.2 stars out of five.

One reviewer, called J&J, wrote: “I am the person a mosquito will find from miles away even in my house. The only one they find in a room of people … I’ve used sprays, foggers, candles, torches .. This is the first time I’ve been able to sit on my patio in peace, even my cat was safe.”

Negative-leaning reviews mentioned that the instructions tell users not to use Patio Shield around food — a big problem for summer grillmasters. Metofluthrin has been graded to be potentially hazardous to people, although CNET reports the potential is “probably low.” Still, it’s also been cited as potentially harmful to bees, birds, fish and cats.

So if you’re simply enjoying a lazy summer evening, and not a cookout, the Patio Shield could help enhance the relaxing vibe.

For the best results, Thermacell recommends letting the Patio Shield warm up for about 15 minutes before you settle in. The metofluthrin mats last for about 4 hours each, offering plenty of time for a game of cards or a book-reading session.

Right now, certain colorways of the Patio Shield are marked down at Amazon and going for as little as $19.45. Packs of mat refills are available, too, so you can easily stock up for the summer.

Here’s a video from Thermacell showing how it works:

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