The woman standing in line at the drugstore had a question for the clerk. “You see this gadget thing?” she asked, holding out a small disk encased in plastic. “It says it’s a carbon monoxide detector. But I need one that detects carbon monoxide gas. Does this one do that too?”

The clerk regarded her with eyes as blank as a dead TV set.

The woman tried again. “Does this just detect carbon monoxide, or does it also detect carbon monoxide gas?”

The clerk finally had to respond. In a monotone he said, “It just does what it says on the back.”

The woman turned the package over and began reading through the immense block of text. Midway through she shook her head unhappily. “It doesn’t say anything at all about gas. It just keeps saying carbon monoxide.”

I couldn’t stand it anymore, so I blurted out, “Carbon monoxide is a gas.” They both turned to me. Neither one looked friendly, but I bashed on anyway: “It’s a gas. It’s not like kryptonite, for God’s sake. It doesn’t lie around your house in slabs. It is a gas.”

The clerk’s eyes were focused on me in a laserlike stare of contempt. The woman said to me with exaggerated patience, as though addressing a particularly annoying and dull-witted child, “This says it detects carbon monoxide. But I need a detector for carbon monoxide gas.”

The clerk said with something close to triumph, “Then I guess it’s no good for that, then.”

The woman returned the package to the rack and left the store.