While there are already electronic devices that detect toxic gases, they can be expensive, and require training to properly use. Soon, though, there could be a cheap and simple alternative – threads woven into washable clothing, that change color when nasty gases are present.

Led by Prof. Sameer Sonkusale, a team at Massachusetts' Tufts University infused regular pieces of thread with three types of dye: MnTPP, bromothymol blue, and methyl red. The first two change color when exposed to ammonia gas, while the third reacts to hydrogen chloride.

Each thread was first dipped in one of the dyes, after which it was treated with acetic acid – the latter step caused the fiber to swell, and made its surface coarser, which may have allowed for better binding of the dye to the thread. In a final step, an organic polymer known as polydimethylsiloxane (PDMS) was applied to the thread – this created a flexible and water-repellent yet gas-permeable seal around the dyed fiber.

When subsequently tested, the treated threads responded to gas concentrations as low as 50 parts per million, by reliably and consistently changing color. This even proved to be the case underwater, where the fibers were able to detect dissolved ammonia. In fact, even after repeated washings, the PDMS coating kept the dye from leaching out of the thread, which continued to function as a gas sensor.

And while the color-changes could simply be assessed by the human eye, it is suggested that for a more precise analysis, a smartphone's camera and an accompanying app might be used.

It is hoped that once the technology is developed further – utilizing more dyes, capable of detecting a wider range of gases – it could be incorporated into clothing used in fields such as oil and gas exploration, public health, the military, or rescue operations.

A paper on the research was published this Thursday in the journal Scientific Reports.