Not all poisonous gases have a smell or a color. But a tiny grid of pastel- and candy-colored squares that effectively "sniffs" out hazardous chemicals in the air such as chlorosarin—a highly toxic nerve agent—could help detect them. Researchers report in ACS Sensors that the colorful patterns in their inexpensive and durable paper-based sensor array changed in the presence of poisonous gases, allowing for quick and accurate measurements within minutes.