$20 is a photoelectric smoke detector to consider. Also sold under the BRK brand, this smoke detector can be used on the same network with pretty much all current BRK and First Alert interconnectable smoke and CO detectors. You don't get the talking technology found in the pricier First Alert models, but there are latching indicators so you can see which smoke/CO detector in the network initiated the alert. However, that viewpoint is not universal. Though, as noted above, Wirecutter does not test basic smoke detectors, they do conduct research that includes talking to fire experts such as Joseph Keenan, assistant fire marshal in Burlington, Vermont, who says that the better approach is to use separate devices so that each can be placed in locations that are best suited to their type. He also notes that, because ionization smoke detectors are more prone to nuisance alarms, if a homeowner disables the device over that which is a very bad idea, by the way they lose all protection.