Standby generators sitting 5 feet from the wall are exactly what the code allows, which is the distance that let carbon monoxide into 105 Louisiana houses after a hurricane knocked the power out and left them running for days

The alarm goes off at half past two in the morning.

Everyone ends up in the hallway in bare feet, and nobody can smell anything at all.

Outside, the machine on the concrete pad beside the bedroom window is doing exactly what it was installed to do, and has been since the storm.

The storm was Hurricane Ida, which came ashore in southeast Louisiana in late August 2021 as a Category 4 and cut power to 1.2 million customers.

The doors are shut. The windows are shut. The house is as tight as it gets.

So the question is not why the alarm sounded, it is how anything from out there ended up in here.

How exhaust from outside gets into a shut house

Exhaust leaves the enclosure hot, and hot air climbs.

Measurements around running units show the plume traveling at least 25 feet from the enclosure, spreading sideways by at least 6 feet, and rising more than 10 feet, past 20 feet when something in the way pushes it up.

That puts it level with the roofline of a single story house.

And the roofline is exactly where a house is built to breathe in.

Under the overhang of almost any roof runs a long perforated strip of aluminum. That is the soffit vent, and its whole job is to pull outside air into the attic.

Dryer vents open the same way, so does the fresh air intake on a central air system, and so does a basement window left cracked in the heat.

None of them can tell the difference between air and exhaust.

The night the detectors went off across a parish

After the storm the power stayed off for days, and everything that could make its own electricity ran around the clock.

The state fire marshal’s office began taking calls about alarms sounding in houses where nothing was burning.

Then calls about people who felt sick and could not say why.

Investigators went house by house, matching who was ill to what was running in the yard.

In one home nine people fell ill on the same night. One of them spent the night in a hospital and eight others were checked and sent home.

A woman whose alarm woke her family said afterward that they had almost lost their entire immediate family and had not known it could happen. Her daughter told reporters you could wipe out generations in one quick breath.

The 256 reports and what was behind them

The storm was Hurricane Ida, which came ashore in southeast Louisiana in late August 2021 as a Category 4 and cut power to 1.2 million customers.

Federal staff collected reports of carbon monoxide exposure from 256 homes in the affected area.

In 105 of them a permanently installed generator was confirmed as the source.

Portable machines were the source in 65 more. In 35 the type could not be determined, and in 52 the source was never identified.

People in 12 of the 105 stationary generator homes had symptoms. Ten of those households never sought care.

No one died in the set.

The work ran four years and produced a 31 page document released in June 2025.

The five foot rule and the twenty five foot recommendation

The installation standard that governs these machines calls for 5 feet between the generator and an opening into the building.

That is the number the installer works to and the permit office checks.

Federal staff now recommend at least 25 feet, and put it in writing to the committee that owns that standard, along with a second recommendation that the engines be built to emit far less of the gas, as the federal report sets out.

Here is the limit of it. A recommendation is not a rule, the standard has not changed, and nobody counted how many of these units are already bolted down, so the size of the exposed group is simply unknown.

A quarter acre lot rarely has 25 feet of side yard to give, which means the setback often lands closer to the neighbor’s bedroom than to the owner’s, as residents told investigators.

The same reliability pressure that sells these machines is showing up elsewhere, in rural towns facing an energy cliff and in data centers buying power protection that burns nothing at all.

What it means for the pads already poured

Put alarms on every level of the house, and keep the unit away from basement windows, dryer vents and soffit vents.

On a big lot that is easy.

On a small one it is close to impossible, and the alarm becomes the only thing standing between the family and the plume.

Every long outage sells more of these machines, and each one is installed to the rule that was in force the day the permit was pulled.

What the Louisiana work established is a mechanism rather than a tally: a plume that goes further and climbs higher than the rule assumed, finding openings nobody thinks of as an inlet.

What it leaves open is the harder half, which is what happens next to the machines already sitting on their pads, waiting for the power to go out again.generators