Pop goes the Chip Bag

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities, and you.

Pop goes the Chip Bag

Transitioning from lower altitude to a higher altitude decreases the pressure on a sealed container. Normally this would be recognized by the bloated appearance of the product in a sealed bag and a rapid release of the pressurized air inside when the bag is opened.  However, if the bag’s seal is weak, the bag can explode with a surprisingly load pop, en route.

This occurred recently on a trip where the altitude changed from 1248 feet to 7500 feet. Taking the temperature difference into account, the external air pressure changed from 14.08 psi (97.8 kPa) to 11.25 psi (77.6 kPa). This resulted in the decrease in external pressure of 2.83 psi (20.2 kPa or 78.3 inches of water) – sufficient to explode the weak seal.

Surprisingly, this wasn’t the only time that a bag of the same brand of chips lost its seal during the same trip but previously the bag did not explode. Since several other brand of pretzels and other munchies did not experience a bag failure during many trips, it appears that a little product line pressure testing during packaging is in order to minimize a weak seal.

Air Pressure in a Chip Bag

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Pressure in the Salmon Cannon

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities, and you.

Pressure in the Salmon Cannon

Dams are helpful to control water flow in rivers but they pose a major problem for migratory fish like salmon. The dam restricts the salmon’s ability to swim upstream and spawn. In the United States alone, there are 85,000 dams. To solve the problem, Whooshh Innovations created its Fish Transport System, also called the Salmon Cannon.

With the Salmon Cannon, fish are either manually placed in a tube or slide in via a gravity slide below the dam. Then the soft tubing conforms to the size of the fish so a column of water does not have to be moved. Moving a column of water in, for example, a 1,700 feet project would require 0.433psi/ft x 1700ft = 736 psi.

In contrast, by conforming to the fish, they are essentially pushed through the system using an average of one to two psi. According to Whooshh CEO Vince Bryan III, “The system builds lower air pressure in front of the fish and more behind them with just a single blower motor, working just like a pneumatic tube at a bank.”

Based on independent studies that showed no scale loss, eye damage or other injuries, the amount of pressure safely transports fish from one area to another. The Whooshh tubes can handle a variety of fish sizes but generally transport fish between 2 and 34 pounds. In a typical system, the fish travel between 16 and 26 feet per second or about 18 miles per hour.

Whooshh Fish Cannon

Salmon fed into the Salmon Cannon below the dam transport through a tube to be safely returned to the water upstream, where they can continue their journey to spawn.
Source: The Guardian and Whooshh Innovations.

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Getting the Right Medical Room Pressure

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities, and you.

Getting the Right Medical Room Pressure

With airborne infectious diseases that can easily spread from one person to another, such as the COVID-19 virus, isolation is critical. In a hospital or clinic, an isolation room needs negative pressure to have airflow into the room and avoid pathogens, or germs, from escaping. In addition to viruses, other undesirable contaminants to keep away from the rest of the population and sterile equipment in a hospital include bacteria, fungi, yeasts, molds, pollens, gases, volatile organic compounds (VOCs), small particles and chemicals.

The airflow to create and maintain the negative pressure (vacuum) in the room requires a consistent pressure differential of about 0.01 inch water gauge (in. w.g.) or 2.5 Pascals (Pa).

According to the Facility Guidelines Institute’s (FGI’s) most recent 2018 FGI Guidelines ANSI/ASHRAE/ASHE Standard 170-2017, other rooms that should be negatively pressurized include:

  • Emergency Department Public Waiting Areas
  • Emergency Department Decontamination
  • Radiology Waiting Rooms
  • Triage
  • Bathrooms
  • Airborne Infection Isolation (AII) Rooms
  • Most Laboratory Work Areas
  • Autopsy Rooms
  • Soiled Workrooms or Soiled Holding Rooms
  • Soiled or Decontamination Rooms in Sterile Processing Department
  • Soiled Linen Sorting and Storage
  • Janitors’ Closets

In contrast, protecting the patient and sterile medical and surgical supplies in an operating room requires positive pressure to keep undesirable contaminants outside. The positive pressure room is achieved by pumping in filtered, clean air.

Isolation (Low) vs. operating room (High) pressure

Isolation (Low) vs. operating room (High) pressure.
Source: Minnesota Department of Health

In fact, some portable, headgear-mounted air purifying respirator systems use positive pressure to protect the wearer.

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The Pressure for Ventilators

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities, and you.

The Pressure for Ventilators

In addition to the pressure to get more ventilators, pressure is an integral part of a ventilator’s operation. Breathing involves inspiratory (inhaling) pressure and expiratory (exhaling) pressure and a ventilator has to take the user’s values into account. Peak Inspiratory Pressure or PIP is the maximum pressure inside the lungs during each inhaled breath and the normal range is 25-30 cm H2O. Positive End Expiratory Pressure or PEEP is the amount of pressure left inside the lungs at the end of a breath to keep the alveoli, tiny air sacs of the lungs, open. The normal range is 3-5 cm H2O.

The pressure inside a patient’s lungs depends on the compliance of their lungs. While the suggested range of pressures during ventilation is 20-35 cm H2O with an absolute maximum of 40 cm H2O, someone with damaged lungs may need a higher pressure.

 

Airway pressure and flow waveforms during constant flow volume control ventilation show PEEP and PIP

Airway pressure and flow waveforms during constant flow volume control ventilation show PEEP and PIP.
Source: http://rc.rcjournal.com/content/59/11/1773/tab-figures-data

With pressures below 50 cm H2O (19.7 in H2O or 4,903 Pa) for dynamic measurements, a pressure sensor designed specifically for these low pressures, such as All Sensors’ DLC, DLLR, and others, provide the required accuracy.

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