The 'who' and 'why' behind siren testing

Q Why are tornado sirens tested on Wednesdays, and why was 1 p.m. selected? Who sounds them?

A Officially they aren't tornado sirens anymore, but outdoor emergency sirens, said Todd Krause, warning meteorologist for the National Weather Service in Chanhassen. They can warn of hazardous-material spills, floods, even power-plant malfunctions. And they are intended to be heard by people outdoors, not necessarily indoors, he added.

Historically, monthly sirens were not sounded in Minnesota until the 1960s, when the federal government constructed and implemented the outdoor warning system. The mandate was that Minnesota test the sirens on the first Wednesday of every month. The state complied to continue receiving federal stipends to fund the warning system.

A 1 p.m. test time was chosen because early afternoon is when the most people would be out and about and likely to hear an outdoor siren. In addition, it wouldn't interfere with the common small-town practice of sounding a noon lunchtime siren.

Because this week was Severe Weather Awareness Week, sirens were to sound twice on Thursday, but because of storms, many counties did not sound the alarm. The idea was for people to practice tornado drills at work and school when the early siren sounded and at home during the later one, said Doug Neville, a spokesman for the Minnesota Department of Public Safety.

Each county is responsible for sounding its sirens, Neville said, adding that one button sets off all the sirens for an area. In an emergency, the county's incident commander -- the police chief, sheriff or county emergency manager -- makes the decision to sound the sirens.

If you hear a siren, go indoors, get to a TV or radio and find out the nature of the emergency before acting. You don't want to go to the basement in a flood, for example.

Shingle clarification Monday's Fixit column stated that new shingles can be installed over existing shingles, sometimes up to three layers on a roof. That's no longer the case. Minnesota's Building Code and Standards changed last year. Minnesota, designated a moderate to severe hail exposure state, now limits the number of shingle layers to no more than two, depending on where you live.

Only one layer of shingles can be covered with a new layer in most, but not all, counties in the northern half of the state. In other words, roofs can carry no more than two layers of shingles.

In roughly the southern half of the state, new shingles cannot go over an existing layer of shingles. The shingles must be torn off and the roof cleared to bare wood for new installations.

To learn what is allowed in your area, contact a local building official.