Isolation room w bed

Negative Pressure Rooms

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Negative Pressure Rooms: Protecting People

Negative Pressure Rooms are used primarily in hospitals and bio-tech facilities to ensure staff and patients are safe from cross contamination from airborne disease and other potentially dangerous contaminants. Negative Pressure Rooms are very different from standard cleanrooms whereas standard cleanrooms are designed to push air out when an air lock is opened, or have “positive pressure” at all times.

In a hospital setting, certain populations are more vulnerable to airborne infections including immune-compromised patients, newborns and elderly people. Of course, hospital personnel and visitors can also be exposed to airborne infections as well.

A negative pressure room in a hospital is used to contain airborne contaminants within the room. Harmful airborne pathogens include bacteria, viruses, fungi, yeasts, molds, pollens, gases, VOC’s (volatile organic compounds), small particles and chemicals.  This is just part of a much larger list of airborne pathogens present in a hospital or laboratory environment.

Rooms that should be negatively pressurized according to The 2014 FGI Guidelines/Standard 170-2013 include:

  • ER waiting rooms
  • Radiology waiting rooms
  • Triage
  • Restrooms
  • Airborne infection isolation (AII) rooms
  • Darkrooms
  • Cytology, glass washing, histology, microbiology, nuclear medicine, pathology, and sterilizing laboratories
  • Autopsy rooms
  • Soiled workrooms or holding rooms
  • Soiled or decontamination room for central medical and surgical supply
  • Soiled linen and trash chute rooms
  • Janitors’ closets

A negative pressure isolation room is commonly used for patients with airborne infections. For example, a patient with active/live tuberculosis, a disease caused by the bacteria Mycobacterium tuberculosis, will be placed in a negatively pressurized room because the tuberculosis bacterium is spread in the air from one person to another.

Using a negative pressure room can better contain the bacterium within the room.

Negative Pressure Room Basics

In a Negative Pressure Room, once an airlock is opened, air is only permitted to enter the room so any contaminants in the room can not escape. Constant vacuum pressurization inside a Negative Pressure Room allows it to maintain the suction at a specific pressure rating; thereby protecting anyone outside of the room from contaminants that could escape from inside the room.

Negative Pressure Rooms are nothing new. In fact a typical bathroom with a closed door and exhaust fan running is a type of Negative Pressure Room. In hospitals, however, the setup is much more complex and much, much cleaner. In hospitals, negative pressure is maintained by balancing the room’s ventilation system so more air is mechanically exhausted from a room than is supplied by the exterior/surrounding building HVAC system. When constructed correctly, this creates a ventilation imbalance, which the room ventilation compensates for by continually drawing air in from outside the room.

In a well-designed negative pressure room, this air is pulled in under the door through a gap. This gap is typically about half an inch high. Other than this single gap, the room is almost always air tight to prevent air from being pulled in through undesired cracks and gaps, i.e. around windows, light fixtures and electrical outlets. Leakage from these areas can compromise (or eliminate) room negative pressure, even if the system is balanced to achieve it. Think of these as small holes in the hull of a boat; eventually it will matter, even if the largest of them is plugged.

Overall, the minimum pressure difference necessary to achieve and maintain negative pressure that will result in air flow into the room is actually very small (0.001 inch of water gauge/ “w.c.). The actual level of negative pressure differential will depend on the difference in the ventilation exhaust and supply flows and the physical configuration of the room.

If a room is well sealed, negative pressures greater than the minimum of 0.001 inch of water are easily accomplished. However, if rooms are not well sealed, as typical with many facilities (especially older buildings with retro-fitted negative pressure rooms), achieving higher negative pressures may require exhaust/supply flow differentials beyond the standard ventilation system’s capacity. In these instances, contractors may have a custom Heating, Ventilation, Air Conditioning (HVAC)/air handler system designed to accomplish the desired result using multiple standard air handlers and filtration systems.

To establish negative pressure in a room that has a normally functioning ventilation system, the room supply and exhaust air flows are first balanced to achieve an exhaust flow of either 10% or 50 cubic feet per minute (cfm) greater than the supply (whichever is greatest). In 90% of cases, this specification should achieve a negative pressure of at least 0.001 inch of water. If the minimum 0.001 inch of water is not achieved and cannot be achieved by increasing the flow differential (within the limits of the ventilation system), the room most likely has some form of leakage (e.g. through doors, around windows, plumbing and equipment wall penetrations), and action should be taken to inspect and seal the leaks. Finding these leaks is accomplished using a simple smoke test (see below) in the room.

Negative pressure in a room can be altered by changing the ventilation system operation or by the opening and closing of the room’s doors, corridor doors or windows. Some rooms are outfitted with special plenums that can be electronically opened and closed based on digitally-acquired feedback systems that monitor the rooms environmental conditions.

What is a smoke test?

A smoke test is a simple procedure to determine whether a room is under negative pressure. The smoke tube is held near the bottom of the negative pressure room door and approximately 2 inches in front of the door. The tester generates a small amount of smoke by gently squeezing the bulb. The smoke tube is held parallel to the door, and the smoke is exhausted from the tube slowly to ensure the velocity of the smoke from the tube does not overpower the air velocity. If the room is under negative pressure, the smoke will travel under the door and into the room. If the room is not under negative pressure, the smoke will be blown outward or remain stationary.

Monitoring Negative Pressure Rooms

As important as maintaining negative rooms pressure, is continuously monitoring the systems which enable it. Without constant monitoring and validation, there is no immediate or physical way to verify proper room negative pressure levels. Even the slightest variations in air flow and variables that may affect it can severely disrupt proper pressurization, and potentially endanger staff, room personnel, and other innocent populations. A complete solution for monitoring negative room pressure would include functionality that would allow operators to quickly glance at a color display that reported both current room variables as well as historic room variables. These are sometimes referred to as “data loggers.” Additional features would include immediate reporting of room conditions such as temperature, relative humidity (RH) and room pressure.

If levels fall below or rise below specified values, becoming ‘unsafe’, a room alarm would notify personnel. Additional warnings would include a way to receive SMS/text alerts, email warnings and automated phone alerts to parties involved directly with the compliance and daily operation of the negative pressure room.

Cleanroom w 3 workers

Clean Room Design: Pharmaceutical

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Cleanrooms: Determining the scope

Most cleanrooms utilized for pharmaceutical use a class range to express cleanliness, Class 100 to Class 100,000. Cleanliness class is determined by particulate counts using a particle counter. Some areas without an official cleanliness classification are considered “controlled environments.”

In essence, a cleanroom is much like any other room; except that instead of containing typical levels of pollutants and contaminants, it is void of damaging particles, bacteria and molds. A few basic modifications could essentially convert any interior room in an office or commercial property into a cleanroom facility. The level of cleanliness determines the classification; which is determined by a international standards organization (ISO) level or United States Pharmacopeia (USP) (if pharmaceutical).

Maintaining cleanliness

Maintaining cleanliness in cleanrooms or controlled environments is dependent on several factors. These include filtration, air exchange rate, pressurization, temperature control and humidity control. While controlling these variables is important, it is equally important to consistently monitor these conditions.  Without continuous monitoring it is impossible to determine whether a cleanroom maintains its class level.

Filtration – See separate posts on filtration.

Air exchange rate – The air change rate, or rate by which the air in the room is completely recycled is controlled by the custom Heating ventilation air conditioning (HVAC) system. Specially designed air handlers move air, calculated in Cubic Feet per Minute (CFM), at a rate that completely “changes” the room air within a specified period of time – typically measured in minutes. This is quite different than ordinary rooms which may completely recycle the air in several hours.

Another point of consideration in both pharmaceutical cleanrooms and bio-tech cleanrooms is the air flow pattern. Non-unidirectional flow cleanrooms rely on air dilution as will as a general ceiling to floor airflow pattern to continuously remove contaminants generated within the room. Unidirectional flow is more effective in continuously sweeping particles from the air due to the piston effect created by the uniform air velocity.

The desired air change rate is determined based on the cleanliness class of the room and the type of operations to be performed in the room. An air change rate of 10-25 per hour is common for a large, low density Class 100,000 (M6.5) cleanroom whereas a class 10,000 (M5.5) cleanroom typically requires 40-60 air changes per hour.

In unidirectional flow cleanrooms, the air change rate is generally not used as the measure of airflow but rather the average cleanroom air velocity is the specified criterion. The average velocity in a typical Class 100 (M3.5) cleanroom will be 70-90 feet per minute, with a tolerance of ±20% of design airflow being acceptable.

Pressurization –  A pressure differential should be maintained between adjacent areas, with the cleaner area having the higher pressure. This will prevent infiltration of external contamination through leaks and during the opening and closing of personnel doors. A minimum over-pressure between clean areas of 5 Pa (.02 inches of water column (in. W.C.”)) is recommended.

The pressure difference between a clean area and adjacent unclean area should be 12-14 Pa (.05 in. W. C.).  Where several cleanrooms of different levels of cleanliness are joined as one complex, a positive pressure hierarchy of cleanliness levels should be maintained, including airlocks and gowning rooms, so that a greater pressure differential is maintained between rooms adjacent ambient air  Note that for certain process it may be desirable to have a negative pressure relative to surrounding ambient in one or more rooms when containment of the area outside the cleanroom is a major concern. A “room-with-in-a-room” may have to be designed to achieve this negative pressure yet still meet the needs of clean operation.

Temperature – Where occupant comfort is the main concern a temperature of 68-70 F+- 2 F will usually provide a comfortable environment for people wearing a typical lab coat. Where a full “bunny suit” or protective attire is to be worn room temperature as low as 66 F may be required. If the temperature is to be controlled in response to process concerns the value and tolerance should be specified early in the design phase to insure that budgeting is accurate.

Humidity – Humidity requirements for comfort are in the range of 30-60%RH. If process concerns suggest another value it should be specified as soon as possible in the design process. Bio-pharmaceutical materials sensitive to humidity variations or excessively high or low values may require stringent controls.

Airlocks/AnteRoom – This is a room between the cleanroom and an un-rated or less clean area surrounding the cleanroom or between two rooms of differing cleanliness class. The purpose of the room is to maintain pressurization differentials between spaces of different cleanliness class. An airlock can serve as a gowning area. Certain airlocks may be designated as an equipment or material airlock and provide a space to remove packaging materials and/or clean equipment or materials before they are introduced into the cleanroom. Interlocks are recommended for airlock door sets to prevent opening of both doors simultaneously.

Other considerations

Designing a pharmaceutical cleanroom requires strategic planning and consideration. Keeping the controlled environment clean and free from contaminants and particles can be critical; equally important is ensuring a well-thought layout of the room, safety training for workers utilizing the room and monitoring equipment to ensure all room controls are working within industry specifications.

Typically, a cleanroom will have a separate HVAC monitoring system that is tied in to the building management/control system such as BACnet. To monitor humidity, temperature and room pressure, a independent room variable monitor is best practice. Independent instrumentation ensures a fail-safe measure to indicate room variables to workers outside of the equipment warning/monitoring system.

A complete monitoring solution would ideally include a large, well-lit color display that indicated current room condition variables such as room pressure, temperature and relative humidity. If these variables or environmental conditions were out of scope, a room alert/alarm would sound. More robust models would also have available functionality that would alert management staff and personnel via text/SMS, email and automated phone alerts.

Advanced models would also have options for cloud-based connectivity and controls. No matter which solution you choose, it is apparent designing a cleanroom for pharmaceutical use is complex, and involves precise instrumentation, expert contractors and lots of planning. Ultimately, the design and functionality will be based on what operations will take place; however, there are some standards that are common across the board; such as ensuring compliance with industry ISO and USP classifications. Always make sure you use a reputable contractor, and ensure you are using a monitoring solution in the room that is independent of the standard control devices; this will protect you, your company and employees and especially your end-consumers from any potential contamination.

Re-calibrating Sensors

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We are often asked how often sensors should be re-calibrated.  The answer to that simple question is complicated.  It depends, first, on what type of sensor it is.  For example, our digital sensors, which are used to monitor temperature in refrigerators and freezers will not get out of calibration for years.  Many of our customers also use 2di thermistor sensors for the same purpose and they can ‘drift’ over time, although not by much.  Our thermocouple sensors, on the other, hand do drift quite a bit depending on how they are used; what temperatures they are exposed to.

So the first thing to consider is what type of sensor it is and how it is being used.  The 2nd factor, and this is usually the overriding factor is who  the temperature is important to.  For example, some industry associations and regulatory bodies recommend that sensors be calibrated on a regular schedule of their own choosing.  The CDC suggests that thermometers used to monitor vaccine refrigerators and freezers e re-calibrated every year or according to the manufacturer’s recommendation.  Re-calibrating once a year is overkill since all of our sensors should remain in calibration for at least 2 years, but they have a lot of weight with the health care industry.

When we issue a Certificate of Calibration there is always a suggested re-calibration date.  Since we are the manufacturer of the sensors this is the manufacturers recommendation.

Picture of Dennis behind the display table

We attended the Kentucky Pharmacy Association Annual Meeting

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Prodataloggers attended the annual meeting of the Kentucky Pharmacists Association the largest professional organization representing pharmacists in the Commonwealth and has been serving its members since 1879. KPhA is recognized by the IRS as a non-profit, tax-exempt organization.

KPhA is the voice of pharmacists from all practice settings concerning education, policy, legislative, and regulatory matters to shape and improve the future of healthcare across Kentucky and the United States.
The voices of democracy speak loudly, especially when many voices join together. The Kentucky Pharmacists Association offers its members the opportunity to band together with like minded voices to be heard. By uniting members for a single cause, KPhA can benefit pharmacists in all practice settings. We also alert our members on rapidly changing healthcare issues via multiple technologies, publications and educational seminars.

Prodataloggers was proud to exhibit our new Cleanroom monitor along with the TV2 freezer alarm, each of which protects the working environment and storage units where vaccines are stored.  The Cleanroom monitor was setup with a temperature/RH sensor along with a differential pressure sensor showing real time environmental conditions.  The TV2 freezer alarm demonstrated how a wireless temperature sensor could transmit the temperature of a refrigerator from inside the fridge.  The temperature was updated every 20 seconds and logged every ten minutes.

An interesting effect was noticed once the sensor was installed inside the refrigerator.  The fridge itself was a small dorm sized unit with a freezer compartment in the top.  When the sensor was placed in the bottom of the fridge the display read 4.4°C but when the sensor was moved up to the top shelf, near the freezer compartment, it read 1.0°C.  This difference in temperature based on location points up the fact that the temperature inside a refrigerator is not uniform.  A difference of several degrees exists between different areas of the same refrigerator.

Please call or email us if you would like more information on either the fridge alarm of the Cleanroom monitor.

 

Compounding pharmacy

California Board of Pharmacy Compounding and Hazardous Drugs Regulations – Monitoring Positive and Negative Pressure

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Compliance for Compounding Pharmacies

All compounding pharmacies will be required to comply with the pending general regulatory updates in 16 CCR 1735 and 16 CCR 1751 on January 1, 2017. The California compounding regulations have since been finalized, and can be found here: https://www.pharmacy.ca.gov/laws_regs/1735_ooa_clean.pdf.

As of January 1, 2017, all California sterile compounding pharmacies must be compliant with the most recent laws and regulations. Let’s look at some of these regulations and see how to ensure your sterile compounding pharmacy meets (or exceeds) state guidelines. The specific regulations pertain to monitoring and recording positive and negative pressure as well as temperature and relative humidity (RH):

  • Section 1735.1(a)
  • Section 1735.1(j)
  • Section 1735.1(l)
  • Section 1735.6(2)
  • Section 1751.(4)
  • Section 1751.1(6)[a,b,c]
  • Section 1751.1(8)
  • Section 1751.1(11)[c]
  • Section 1751.3(21)

The above sections outline the proper monitoring and recording of negative and positive air pressure as well as general environmental monitoring and the recording of these variables.

A typical clean room consists of an anteroom (or gowning room) and a sterile room (cleanroom). Maintaining the correct air pressure differential between these two rooms is critical in a compounding pharmacy environment for the safety of cleanroom workers as well as related staff.

Monitoring air pressure and controlling air pressure based on the data monitored are separate initiatives. A California State-compliant clean room monitoring system should include the following:

  1. Ability to monitor negative and positive air pressure differentials between multiple areas of interest.
  2. Chart and record collected monitoring data for quick and effortless retrieval upon state inspection.
  3. Store logged data for prolonged periods of time in an integrated/on-board storage array.
  4. Allow for fast and organized download of collected negative and positive air pressure differential readings.
  5. Have the ability to sample in air pressure differential in intervals set by cleanroom administration, and has the ability to change based on sterile compounding needs.
  6. The ability to chart, and log, temperature (±.05°F), relative humidity (RH) (±3%), and differential pressure (±0.007″ WC)
  7. Additional advantageous accessories to the ideal system would include the ability to send alert notifications via text/SMS to all pharmacy personnel, or phone call alerts with an automated phone dialer.  Having an audible room alarm would be a plus.

In most cases, current technological hurdles prevent compounding pharmacies from possessing an “all-in-one” solution. Buying separate system components to monitor all required variables can be expensive and difficult to integrate.

Solutions

While there are many stand-alone products which, when used in combination, can provide complete compliance, it is preferred in most compounding pharmacies to have a single differential air pressure, temperature and relative humidity monitoring solution. There are very few reputable manufacturers who can accomplish this, and even fewer that offer automatic data logging, remote sensors and USA-based manufacturing, R&D, woith live product support. In fact, a company called “Two Dimensional Instruments, LLC is the only company which offers such a solution. This site (prodataloggers.com) is the only authorized distributor of the TV2 Room Pressure Monitor.

TV2 Room Pressure Monitor- An Introduction

The TV2 Room pressure Monitor is the only all-in-one monitoring solution for positive and negative air differential pressure monitoring, temperature and relative humidity monitoring, automatic data logging, with advanced and automated alerts and USA-based manufacturing & support.

The TV2 Room Pressure Monitor features some of the most comprehensive and secure data acquisition, monitoring and reporting capabilities available. The core chipset/brain of the TV2 Room pressure Monitor is in use and trusted by some of the world’s most highly technical (and demanding) companies such as NASA, Boeing, Northrup Grumman, Lockheed Martin, GE and the Department of Homeland Security.

In it’s second hardware revision and tenth software revision, the TV2 platform is a trusted workhorse in the field of aerospace, academia and other institutions where highly-accurate instrumentation is required. The TV2 Room Pressure Monitor exceeds all California Board of Pharmacy requirements concerning differential air pressure, temperature and relative humidity monitoring. Additionally, the TV2 satisfies all data logging and records-keeping requirements with 21-CFR-11 encrypted data storage.

Other features of the TV2 Room pressure Monitor can be found here: TV2 Room pressure Monitor Features

A product spec sheet can be found here: TV2 Room Pressure Product Spec Sheet

If you want to learn more about an example installation, you can view installation notes here https://www.prodataloggers.com/clean-room-installation-guide/

Finally, if you are considering other brands, see how the TV2 Room Pressure Monitor stacks up against the competition here.

If you want pricing information or to ideas in configuring your product, please visit our store!

Buy Now!
TV2 mounted on wall

Using a Permanent Room Pressure Monitor in a Negative Pressure Isolation Room

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Negative pressure isolation room.

Permanent Room Pressure Monitor

Before a new isolation room is occupied, and after the mechanical contractor has adjusted the airflow quantities as directed by the engineer to ensure that it operates as designed it should not be assumed that it will operate under the same conditions for every more. Mechanical systems do drift out of balance over time so it is important to regularly check that an isolation room is still operating under negative pressure; planning for this should be included in the initial design of the mechanical room.

The most reliable way to monitor negative pressure is to install a permanent electronic room pressure monitor as part of the construction project. When properly selected and installed, a room pressure monitor can provide continuous confirmation of negative pressure across a room boundary. This is in contrast to routine periodic smoke testing, which merely provides an indication of directional airflow at the moment of testing. Continuous monitoring can provide instant notification if the pressurization fails or fluctuates during the day.

A well-constructed pressure room monitor consist of two main components: a wall-mounted panel and one or more sensors. The panel is usually mounted on the corridor wall just outside the isolation room suite and displays the pressure difference in units of ” W.C.

The best type of permanent pressure monitors are those which measure and display the actual air pressure difference between the isolation room and the reference space.  A power supply will be required for the panel.

Pressure differentials across room boundaries can be very small, often in the range of thousandths of an inch. For example, the CDC Guidelines recommend that negative pressure be at least minus 0.001″ W.C. Some devices that measure differential pressure are not accurate to this level. Before specifying or purchasing a room pressure monitor, make sure that the device is capable of accurately and reliably measuring a pressure difference this small.

Direct Room Pressure Monitor

To record a differential pressure, two readings are required: the air pressure in the room and the reference pressure in the corridor. A remote sensor to measure the room pressure is installed in the negative pressure room wall or ceiling with a static port opening in the area being compared. Another sensor measures the air pressure in the corridor. The difference in these two pressure values is the relative room pressurization, which is displayed on the panel.

If there is an anteroom between the isolation room and the corridor, the pressure differential to be measured is the one between the isolation room and the ante room. Or in the best case two differential pressures can be measured and displayed.  One between the room itself and the anteroom and another differential pressure reading between the anteroom and the corridor.

The location of the differential pressure sensor can affect the accuracy of the measurement. They should be installed as close as possible to the isolation room door, but away from drafts. A wire from the panel will run to the actual pressure sensor itself and clear plastic tubing will need to be run from the sensor to the static pressure port in each area.  This tubing will typically be run out of sight inside wall cavities and above the ceiling.

Alarm(s) and Controls

In addition to providing a continuous readout of the pressure difference, the wall panel should include an audible and visual alarm to warn staff when pressurization is lost. The alarm will sound when the measured room pressurization drifts to less than the monitor’s reference pressure value. The reference pressure value is programmed by the user. It will be a value between the steady state pressure differential maintained by the room and zero (neutral pressure). For example, in a room with a steady state pressure differential of minus 0.03″ W.C., the alarm could be programmed to activate when the pressure differential rises to minus 0.001″ W.C. Minus 0.001″ W.C. is the reference pressure value.

The wall panel should also allow staff to program a time delay between loss of pressurization and alarm activation. The time delay will allow staff to enter and leave the room without setting off the alarm. A typical time delay is 45 seconds but could be as much as several minutes. The audible alarm is usually a beeping sound, which will stop when negative pressure is restored or when silenced with a screen touch.

The visual alarm usually consists of a red warning light. Most wall panels also have a green “normal” or “safe” light, which indicates that the monitor is operating and negative pressure is within programmed parameters. The best wall panel displays now show the differential pressure in a green font if the pressure is within ‘safe’ limits and in a red font if the pressure differential falls or rises too high.

Like the audible alarm the visual display will reset once the pressure returns to expected levels, however the max/min indication will remain red indicating that the pressure was too high or low at some point since the last time it was checked.

Max/Min Pressures

The best differential pressure monitors have a max/min feature which continually shows the high and low pressure reached since it as last reviewed.  This ensures that someone is regularly checking, not only the current pressure, but is also aware if an unsafe pressure occurred in the past.

Remote Alarm

In addition to the alarm included on the wall panel, most room pressure monitors include an extra relay to trigger an alarm signal in a remote location, such as the nurses’ station, a central switch board, or the engineering department.  The best pressure monitors can be set to send an email or text alert if an alarm occurs. In some states, for example, the hospital building codes require that negative pressure isolation rooms be equipped with an alarm that annunciates at the room and at a nurses’ station or other suitable location.

Commissioning and Staff Training

The monitor installer’s responsibilities should include verifying the operation of the sensor.  The following should be completed before the room is used to isolate suspected or confirmed infectious TB patients:

  1. Verify that the alarm works. Hold the room door open. After the time delay, the audible and visual alarm should annunciate. The alarm should reset after the “mute” or “reset” button is pressed and/or the door is closed again.
  2. Verify that the monitor is correctly reading the pressure. While the door is held open, the pressure reading should be at or near 0″ W.C.
  3. Instruct staff in monitor usage. The floor staff who depend on the monitor for their safety should feel comfortable using it. They should receive detailed instructions on how the monitor works and how it is.
Setra Room pressure Monitor

Review: Setra Room Pressure Monitor

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This post will review the Setra Room Pressure Monitor and show a full feature review as compared to other room pressure monitors.

The Setra SRPM is commonly used in cleanrooms, positive pressure rooms, negative pressure rooms, negative pressure isolation rooms, and in sterile compounding rooms. The Setra SRPM can also monitor temperature (within limited ranges) and relative humidity (RH).

The Setra Room Pressure Monitor Model SRPM is a re-branded product that several other companies have chosen to feature. The Setra SRPM is identical in features and Chinese-based manufacturing you will find in other brands and products such as the:

In this product review, we will compare the Setra to the TV2 Room pressure Monitor in a feature-by-feature comparison table below.

 

[easy-pricing-table id=”1491″]

The complete line of Setra Room Monitoring instruments is popular and well-known throughout the industry. however, there are other comparative options that offer more robust functionality and data logging options. The TV2 Room Pressure Monitor is a great alternative to the Setra Model SRPM.

Both the Setra SRPM and the TV2 Room pressure Monitor are typically used in new construction and post construction applications where differential pressure are monitored. Althought the Setra has a monochrome touchscreen, the TV2 Room pressure Monitor has a full-color QuickCheck easy-to-read large touchscreen with an intuitive menu system.

One of the key features of the TV2 as compared to the Setra is the ability of the TV2 Room pressure Monitor to alert admins by SMS (text alert), by email, and by automated phone alerts with custom messages.

Additionally, the TV2 automatically logs all data and offers complete reporting for environmental conditions, as well as provides remote (LAN/USB) connectivity for monitoring and reporting.

Most consumers would choose the TV2 Room Pressure Monitor due to the wider availability of features and USA-based manufacturing and support.

man in bunny suit under hood

Airborne Infection Isolation Room (AII)

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What are Airborne Infection Isolation Rooms?

Airborne Infection Isolation (AII) Rooms are also known as “Negative Pressure Rooms.” Negative Pressure Rooms are designed for and used by hospitals and pharmaceutical compounding facilities to prevent airborne contamination. In a negative pressure room, or airborne infection isolation room, the HVAC system is designed to exhaust room air and prevent inner-room contaminates from escaping.

The Center for Disease Control and Prevention (CDC) requires hospitals and certain compounding pharmacies to have functional and highly efficient negative pressure rooms. In hospitals, the goal is to prevent the spread of infectious diseases like Tuberculosis, SARS, H5N1, influenza or other communicable respiratory diseases. In compounding pharmacies, negative pressure rooms are used to prevent radioactive and/or chemotherapy compounds from escaping and interacting with workers or bystanders.

How Do Negative Pressure Rooms Work?

Negative pressure in an Airborne Infection Isolation Room is maintained by utilizing an existing HVAC system in a hospital or pharmacy or by installing a standalone air treatment system/air handler unit. The key to maintaining negative room pressure is to balance the exhaust inside the control room with the pressure differential outside of the control room. The minimum typically maintained is -0.01” WC negative differential room pressure.

A consistent flow of suction or negative air pressure exists in the negative pressure room; typically pulling air from under the door (or specialized HEPA filter unit). Room exhaust is wither heavily filtered through HEPA units or into custom duct-work and ventilation stacks in the roof of the negative pressure room. In some cases, atmospheric air is sufficient to dilute to exhausted air.

Typically, the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) determines exactly how negative (and positive) airflow should best be delivered in these spaces. Additionally, ASHRAE Standard 170 specifies accurate air change rates, pressure requirements, temperature and filtration for negative room pressure applications.

Hospitals and pharmacies are encouraged to use a monitoring solution that provides negative and positive pressure monitoring, temperature monitoring and relative humidity (RH) monitoring. This is why so many hospitals and pharmacies trust the TV2 Negative and Positive Room Pressure Monitor. 

modular clean room

OEM Cleanroom Install In One Hour!

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Recently, we met one of our OEM’s at one of their customer’s facilities where they had just built a cleanroom. This was for a pharmacy with an eight bed clinic in a small town in West Virginia. They were just finishing up construction of the room and began installation of the TV2 Monitor for cleanrooms (positive pressure rooms). The installation included the Quick check touchscreen monitor, one temperature/humidity sensor and two differential pressure sensors.

The small cleanroom consisted of one small ante (gowning ) room and the work room, which was divided into two areas separated by a polycarbonate divider extended from the ceiling to about 3.5 feet from the floor.

One TV2 pressure sensor measures the pressure differential between the outside area and the ante-room. The second pressure sensor measures the pressure differential between the ante-room and the clean room. The temperature/RH (Relative Humidity) of the working area was also monitored. All three sensors were mounted above the drop down ceiling with velcro an wired back to the monitor that is mounted on the wall by the door into the gowning area.

Each pressure sensor’s input tubes were connected to a plastic static pressure port mounted to a wall snub.

The entire installation process took one hour and one keyhole saw, which was used to poke a couple of holes in ceiling tiles and through the drywall where the Quick check monitor was mounted.

After the four pieces, the monitor and three sensors were in place and the wires run above the drop down ceiling, each sensor was plugged into the monitor. The monitor automatically recognized each sensor and asked how often we wanted to log it’s data. We then set a high and low alarm for each sensor and we were done. It was quick and easy. The TV2 Room Monitor immediately displayed the current conditions so the pharmacist can see if conditions are safe anytime she enters the room.

The QuickCheck Touchscreen display showed the two pressures were two low with a red font until the fans were turned on and the doors closed, at which time they turned green showing that they were above 0.015″ of water.

Continue Testing of our Pressure Sensor

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In our efforts to continue to test and characterize our cleanroom pressure sensor we built a miniature cleanroom out of a cardboard box and an old computer fan. To improve the ability of this home-made, leaky chamber we sealed the entire box in plastic tape and punched a very tiny hole in the top of the box. These addons certainly did not make the box clean but it did make it possible to create a small positive pressure in the box, which we dubbed “test-chamber A”. The A is for amateur- thrown-together in an hour.

When we powered the fan we were able to generate a positive pressure of between 0.023 and 0.041″ of water. Our Cleanroom pressure sensor, which we installed with a passive wall plate, was able to correctly display and log the readings over several days. It responded immediately to changes in the pressure when the fan was turned off, going to 0.000″ within about 20 seconds. Once the fan was turned by on the pressure built up to the expected 0.030″ within a minute.

One thing we noticed was that the pressure bounced back and forth a bit reflecting the changes in pressure as air escaped through not only the pin hole in the top of the box but also through the fan itself. This very much reflects what happens in a normal sized clean room. The only way to stop the fluctuation would have been to cover the fan and the pin hole once the pressure had built up. Assuming the box was completely sealed the pressure would have stabilized at some value. Actual cleanroom pressures bounce around a bit also as air escapes through door frames, around fan enclosures and other minute openings. This is normal and is reflected in the pressures displayed on the QuickCheck monitor. It is possible to buffer the pressure a bit by averaging the pressures, which is allowed by the 2di CleanRoom monitor. The average setting can be changed on the sensor setup menu to fast, medium or slow. Setting the averaging to medium or slow would cause the displayed pressure to be a little more stable. However, bear in mind that we are measuring very small pressures, down to thousands of an inch, so any small change in the environment will cause a change in pressure

Step two was to test the QuickCheck display, which we did by setting the alarm pressure to 0.010″.

QuickCheck display showing low pressure reading

. Once the fan was turned off the pressure reading turned red indicating that it had dropped below our alarm threshold. And after 10 minutes the alarm sounded, the screen flashed, and an email message was sent showing that the pressure had fallen below the safe threshold.

We did not hook the strobe up of this test but had it been in place the strobe would have begun flashing. The ten minute delay in the alarm was set in the alarm menu to eliminate false alarms which might occur if the door had been opened. (Not a likely scenario for our miniature cardboard box). This delay feature is very important for our customers who do not want to be texted every time someone opens the door causing a drop on room pressure.

Our very limited testing has verified that the 2di CleanRoom pressure sensor can pick up very small changes in pressure and responds in every way expected.