Effective today, contractors will be required to install carbon monoxide alarms into all multi-dwelling units, such as apartments. The law is a further update of a law that took effect in July 2011, which required installation in all single-family housing structures, according to Barbara Bashall, executive director of the Nevada County Contractors Association. Unlike many of the regulations that are implemented by the state of California every three years, the new law will not be financially onerous for contractors or homeowners, Bashall said. Each year in the United States, an average of 450 deaths and more than 20,000 emergency room …