WASHINGTON — Nearly a half million Kidde dual smoke alarms have been recalled because of an issue that stops them from detecting smoke.

A yellow cap left on a sensor in two models, PI2010 and PI9010, during manufacturing is the problem. The date codes on the affected units, which can be found on the back, are Sep. 10, 2016 through Oct. 13, 2017 for both models. Users can look through an opening on the side of the unit for the cap.

The PI9010 is a battery-powered unit, while the PI2010 is hardwired and runs off the home's AC power. Around 452,000 units were sold in the United States.

If you have either unit, call Kidde toll-free at 833-551-7739 from 8:30 a.m. to 5 p.m. EDT Monday through Friday, and from 9 a.m. to 3 p.m. on Saturday and Sunday to arrange for a replacement.

The company said users should not attempt to open the case and remove the cap.

The smoke detectors were sold between September 2016 and January 2018 for between $20 and $40 at Home Depot, Walmart, and other stores, as well as Amazon.com.

One incident of the yellow caps still being in place was reported to Kidde. No injuries were reported.