Thermostats with digital displays typically do not contain mercury switches. Switches containing liquid mercury are found in older wall-mounted thermostats. Although these switches are fairly sturdy, they should be carefully handled to avoid breakage. In addition to municipal collection programs, mercury-type thermostats are accepted at no charge at many plumbing retail stores (search Yellow Pages under “Plumbing Supplies). For more information, go to www.thermostat-recycle.org.