Following the Clues of Carbon Monoxide Exposure

Too often important questions are never asked in identifying CO as in the Madison Apartment Carbon Monoxide Exposure. Carbon monoxide poisoning must be ruled out first.

By Rebecca Martin

Our blog last week about the Bahamian Sandals Resort preceded findings that carbon monoxide exposure had been the culprit in the death of three tourists  There had been clues in the limited news stories which should have raised questions about a possible carbon monoxide exposure?

  • Why two unrelated couples lodged in the same building had become ill within the same timeframe and sought medical care?
  • Why the emergency room had released both couples assuming food poisoning without confirmation?
  • Why emergency responders had ruled out carbon monoxide exposure without divulging how this had been determined or how long after the incident especially considering how levels may have dissipated merely by the rooms being opened and ventilated by emergency crews?
  • Especially troubling was the question of whether the guests were returned to the same rooms after becoming ill and why?

In epidemiological events, carbon monoxide exposure must be ruled out as a matter of course. Too often investigations only scratch the surface as to the cause of illness which can lead to death. Carbon monoxide poisoning and its SOURCE and PATHWAY must be ruled out first.

So it was no surprise to discover that carbon monoxide exposure had indeed been the culprit. The clues were there.

This week a new potential carbon monoxide exposure story raises some disturbing questions as well. According to the City of Madison, Wisconsin Fire Department website, a carbon monoxide incident Monday evening caused the evacuation of a 128 unit apartment building close to the UW Madison campus. Dangerous and potentially lethal levels of carbon monoxide had been found at the location on University Avenue.

The initial call came from Madison Gas & Electric who had detected levels at 500 ppm[1] on an upper floor and 250 ppm on lower floors. The initial determination of the source of this build up was a carpet cleaning service van which had been left running outside an exterior stairwell door. Was there a portable electric generator running inside of this service van?

Why Highest Carbon Monoxide Exposure Levels on Upper Floors?

The described scenario brings up questions immediately. Carbon monoxide is basically the same weight as air. Oxygen and nitrogen which makes up the air we breathe weighs in at 28.013 while carbon monoxide weighs 28.011. Carbon monoxide does not rise unless it is carried by hot air moving upward or by some other form of atmospheric condition.

So why would higher concentrations of carbon monoxide be measured on the upper floor of the building? The answer could exist in the stairwell itself. Some taller buildings have pressurization capability.

“This is where a stair shaft is fed by supply fans that activate during a fire, creating a positive pressure within the shaft so fleeing occupants are not followed by smoke entering the stairs behind them.”

Theoretically such a situation might cause carbon monoxide to be carried upward if fire doors to the stairwell were left open. This is particularly true if the door at the bottom of the stairwell has been propped open. In this case, pressurization fails and in the case of a fire, carbon monoxide will be carried along with smoke to the upper floors. But this is in case of fire where carbon monoxide will ride the warmer air currents upwards.

Was a Blocked Exhaust Flue the Cause?

What did cause the upper floors of this apartment building to register higher levels of carbon monoxide from a ground-level, non-fire related source? Unless the presumed source was not the cause of the carbon monoxide. In our experience, CO highest on the upper floors is more likely related to a leak or blockage in the chimney or flue.

How Long Did Madison Carbon Monoxide Exposure Persist?

There is another clue which raises questions. Firefighters noted that several carbon monoxide detectors had been tossed into the hallways with batteries removed. They had photographed some of them at the sight once the building had been ventilating through the use of fans. Evidently tenants had become annoyed with the sound of carbon monoxide detector alarms and discarded them in the hallway. I try to visualize this scenario.

It seems unlikely that the tenants on the most impacted floor where levels measured at a potentially fatal level of 500 ppm would simultaneously choose to ignore the alarm sounding and immediately place them in the hallway? A carbon monoxide detector will take 4-15 minutes to alarm at these levels. The most likely symptoms for a healthy adult would be headache, fatigue, dizziness and fatigue within one or two hours. Even though no one appeared to need hospitalization at the scene, it is possible that with this level of exposure, residents may get sick over the upcoming days. For more on the delayed effects of carbon monoxide poisoning, click here. 

“At sustained CO concentrations above 150 to 200 ppm, disorientation, unconsciousness, and death are possible.”

But what motivated residents to ignore the first warnings of the carbon monoxide detectors and remove the batteries and place them in the hallways? According to gas

While the exact short and long term carbon monoxide levels recommended by ASHRAE, OSHA, NIOSH and other organizations differ, the consensus is that

  • 9 ppm (parts-per-million) is the maximum indoor safe carbon monoxide level over 8 hours
  • 200 ppm or greater will cause physical symptoms and is fatal in hours
  • 800 ppm of CO or greater in the air is fatal within minutes

Alarms without Batteries Points to Continuing Carbon Monoxide Exposure

Did the residents ignore the alarms for an hour or two and then become so annoyed as to remove the alarms? Or were alarms sounding prior to the arrival of the carpet cleaning service? At 500 ppm, we can safely assume that the alarms would not be sounding for 8 hours without serious consequences. As it was, two people were treated by emergency responders at the scene and the rest were able to return to the building after it had been properly ventilated.

At those levels, almost everyone’s CO detectors would have been blaring at once. In our experience, when multiple people become aware of a simultaneous threat, they tend to figure out something dangerous is happening.

Alarms would not have been sounding due to the normal carbon monoxide concentrations in residences. Most carbon monoxide detectors today sound at 50 ppm after 8 hours and 70 ppm at 1-4 hours. Ideally the carbon monoxide levels in homes should be equal to the levels outside. The federal standards are a maximum of 9 ppm, but the concentrations vary in different areas. For instance, according to the Minnesota Department of Health, air quality in the Minneapolis area ranges from 0.03 – 2.5 ppm. There is no safe level of carbon monoxide but anything above 9 ppm is considered unhealthy for prolonged exposure, especially for those with health issues.

Alarms Only Sound When There is Danger

Carbon monoxide detectors are not going to sound at acceptable levels of carbon monoxide regardless. The questions remain. Did the residents remove carbon monoxide detectors immediately when alarms sounded or were these actions motivated by carbon monoxide detectors routinely sounding over a longer period of time? If the latter is true, could there have been another source involved within the building itself?

If residents had ignored initial warnings from carbon monoxide detectors, how long were people exposed to levels of carbon monoxide capable of impacting health? Certainly at 250-500 ppm, there could be immediate and long term damage possible following the removal of the carbon monoxide detectors by certain tenants. None of the tenants were sent to the emergency room for testing and only two were treated at the scene, presumable with oxygen. But we do know that the effects of carbon monoxide poisoning can take days, weeks or months to appear.

The Madison Fire Department posted on Twitter reminding people not to ignore carbon monoxide detector alarms and certainly not to remove them. While firmly supporting that statement, there is still a big question as to why the tenants had 1) decided to remove them instead of responding and 2) removed them because it was not unusual for the detectors to sound alarms previous to the incident on Monday.

Two days later, we continue to have concerns that unanswered questions may still leave these Madison residents at risk.

[1] 500 ppm is a deadly level.


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