Who Watches the Watchers? (2): Self-cleaning Ovens

Consumer Reports posted the second volume of their own blunders. Most of them aren’t strictly human factors (though still worth a read), but one stands out:

But can he bake a cherry pie?
One of our engineers told us that he received a call from his wife to clean the oven while she was out running errands. He relayed the orders to his son to start the oven’s self-cleaning mode. The son followed the orders dutifully but didn’t check the oven to see whether anything was stored inside. A short while later, smoke began pouring from the oven and the kitchen glowed from the light of the plastic cutting board burning inside.

Our engineer tried to turn the oven off but discovered that once the self-cleaning mode had been started, it couldn’t be stopped. Quick thinking prevailed—he went to the circuit breaker box and shut off the power. The oven, however, remained locked and the cutting board continued burning. It took the local fire department to pull the range out of kitchen and put it the driveway for the fire to finally burn out. Even then, the door could not be opened until the oven had cooled down.

That’s probably the last time our colleague will be asked to clean the oven. And it left us wondering why there’s no emergency override that would shut down the self-cleaning cycle.

I am so frightened of the commitment of the self-clean cycle that I’ve never used it for any oven. I just move houses when the oven gets too dirty. (I’m kidding, but it’s close to the truth.) I’m also scared of anything that hot being inside my house without being inside my chimney.

The reason ovens lock during a self-clean is temperature: it’s getting hot enough in there to burn away residue and you don’t want to accidentally open the door and be blasted. However, I can’t think of any reasons not to stop it mid-clean and have it remain locked until it cools down enough to be safe. My best guess is that older ovens were built with no way to sense temperature (the earliest ovens had an analog dial that operated in an open-loop system – you had to measure the temperature yourself and turn it up or down accordingly.) With no way to sense that the oven cooled sufficiently, the only way to be safe is to lock it until the cycle ended and a cool down time passed.

We’ve had closed-loop ovens that sense their own heat levels for a while now, so my second best guess is that the ovens still locked due to tradition. Some ovens have sensors specific to the cleaning cycle to shorten the self-clean time (though no mention is made of an emergency stop). Feedback can be a wonderful thing.

An override for the self-clean cycle would be wonderful too.

Podcast: Design for the Real World (Studio 360)

Studio 360 is a great public radio show hosted by Kurt Anderson about “what’s happening in pop culture and the arts.” Don’t let that description fool you, it’s not “Entertainment Tonight.” Instead, the show focuses on interesting stories and interviews about a variety of topics.

Every few weeks, they have a segment called “Design for the Real World” where a guest talks about the design of some product or system.  Happily, I recently discovered that these segments have their own separate podcast.  For example, a recent fascinating one was a photographer talking about the design of a Leica camera.  Another great one was a segment on interstate highway signs.

Patient photos aid docs reading faceless CT scans – Yahoo! News

Here is a really neat study that found that adding a picture of a patient’s face on a CT scan caused doctors to be more careful when examining the images.  The researchers proposed mechanism for the effect is that the faces induced doctors to have more empathy for the patient which led them to more carefully analyze the images.  Whatever the mechanism ends up being, it really shows the power of simple changes in the task/interface leading to practically relevant differences in performance.

The study’s focus was not on the ailment the scans were meant to evaluate, but rather on incidental findings that often show up on CT images, such as kidney cysts in patients scanned for suspected appendicitis. Doctors reported these extra findings in 81 scans when the photos were included.

Three months later, the doctors unknowingly viewed the same 81 scans, but without patients’ photos. This time, the doctors failed to report 80 percent of the incidental findings.

Patient photos aid docs reading faceless CT scans – Yahoo! News