As the economy slowly re-opens, businesses need to plan for restarting
operations. Those who require their staff to work in a common location will
need to ensure their employees, customers and partners feel safe and can
trust that they will be returning to a healthy and clean work environment,
both for the near future and for potential second or third waves of infection.

The spread of COVID-19 is generally understood to be through close proximity – by both droplets (within 1-2 meters) and surface transmission. There is little evidence at this time to support airborne transmission, but there is also no definitive proof it is not a contributing transmission path – transmission through HVAC systems is not adequately tested or documented and available resources (such as ASHRAE) appear to favour an abundance of caution in making any recommendations due to this lack of testing.

Our engineers and technology strategists have been exploring the impact of COVID-19 on building design. Here are some considerations for building owners and tenants.

Improving Air Quality

In a typical office building, indoor air is comprised of roughly 25% outdoor air. The rest is recirculated and filtered. It will be important to understand what upgrades may be necessary for the building’s HVAC and Building Automation System (BAS), as well as current and emerging technologies to enhance these systems.

Simple building operation and system adjustments

A first stage of re-entry can include the following, relatively simple adjustments to normal building operation:

  • Assess the amount of additional outdoor air for occupied and unoccupied modes of operation to permit increased air exchange in the tenant areas and disable demand-controlled ventilation schemes.
  • Review the volume of additional outdoor air that could be added to the system based on current system capacity and further open outdoor dampers to eliminate or reduce recirculation. In milder weather, this does not necessarily
    affect thermal comfort or humidity, but will become more difficult in extreme weather.
  • Assess the site for possible addition of energy recovery units to offset some of the operational costs associated with an increase in outdoor air.
  • Make necessary adjustments to building control sequences and changes to set points, such as humidity, to allow for temporary flushing or extended operation of systems.

Design and selection of various filter options for your air handling systems

  • Investigate solutions to retrofit or add enhanced filter technologies in existing air handling systems such as higher MERV-rated filters, High Efficiency Particulate Air (HEPA) filters, Active Particle Control filters, UVGI, and Bipolar Ionization.
  • Consider portable room air cleaners with HEPA filters.
  • Active Particle Control technology filters are claimed by their manufacturers to create collisions on a sub-micron level. This causes smaller particles to collide and stay together becoming larger, and providing the ability to collect the larger particles within normal MERV 13 or higher filters.
  • Consider ultraviolet germicidal irradiation to safely and effectively reduce bacteria, viruses and allergens, particularly in high-traffic areas such as lobbies, elevators, and cafeterias/kitchens.
  • Bipolar Ionization may also be a beneficial solution to improving air quality. Manufacturer literature states that it inactivates viruses and creates positively and negatively charged ions that attract to other particles and become bigger and heavier. These bigger heavier particles can now be better trapped by MERV 13 or higher-rated filters. Also, many small particles that are generated within a space will drop to the floor quickly, taking them away from where we breathe. It is imperative to understand that the above changes to system operations and addition of certain filter technology will have an associated impact to energy use and cost.

Cleaning of systems

  • Consider probiotic cleaning of existing coils and other components in contact with air streams.
  • Consider swabs of air handling unit interiors after cleaning and instantly test for presence of Covid-19.
  • Consider use of mobile and local air-cleaning solutions in congested areas.
  • Re-start and re-establish safe drinking water supply.
  • Establish process, protocols, and testing requirements for domestic water systems that have been stagnant during the COVID pandemic.

Technologies for Infection Control in Buildings 

There are various technologies currently in use or emerging in the healthcare sector that could benefit and be applied to commercial real estate buildings.

Real-time locating and monitoring systems

  • Hand hygiene compliance–technology such as infrared can be used to better monitor hand hygiene. Can be deployed at hand-washing stations and bathrooms.
  • Contact tracing apps can create a contact history log, based on location. They can allow you to accurately track the interactions between people, the facility and equipment. Knowing this information can help to slow the spread of the infection. However, there are privacy implications involved with contact tracing apps which should be carefully considered.
  • Occupancy sensors provide real-time information on occupancy and location to indicate whether social distancing or occupancy limits are being respected.
  • Building owners and tenants can also send instant communications and alerts through a mobile app to occupants, and provide information to first responders in case of emergencies, including specifying the exact location of the emergency.


  • UV lighting technology has improved to the degree that it can sanitize an unoccupied room in a few hours.
  • Cleaning robots (currently used in some hospitals) may become normal procedure to clean office buildings or hotels in off-peak hours.
  • Occupancy sensors can notify cleaning crews (or the aforementioned robots) that a particular area is vacant and can be sanitized before next use.

Touchless (Hands-free) control

  • To minimize potential infection from contaminated surfaces, occupants could utilize mobile apps (through their smartphones) to control security access/opening doors and elevator call. This could be rolled in with existing space management apps used for boardroom booking and office hoteling – which also play a role in effective social distancing.
  • Automated or proximity sensor door opening technology.

Social distancing

  • To better practice social distancing in the office environment, occupants may prefer to access amenities such as ordering food, dry cleaning notification, building gym occupancy, transit alerts and ride sharing services through an app – possibly one provided by the building owner that integrates in-building amenities and other local services.
  • Automated social distancing alerts through wearable technologies or smartphone apps.

How HH Angus Can Help

Whether you are a building owner or tenant, we can help you plan your operational restart strategy. Specifically, we can:

  • Assess your HVAC systems and explore ways to minimize the impact of virus aerosols.
  • Work with the Facilities team to appropriately optimize building systems and controls.
  • Investigate and recommend technologies that can help mitigate the spread of infectious disease through sanitization, monitoring, social distancing and other means.

HH Angus has been involved in the design of healthcare facilities (both new construction, renovation/retrofits, expansions and maintenance) for over 75 years. We are a leader and innovator in all aspects of healthcare design. Our knowledge of hospital design and how to address challenges such as infectious disease control can be effectively leveraged into other sectors such as office buildings, retail, hospitality, educational facilities, airports, transit stations, entertainment centres and more.

As well, many of HH Angus’ technical staff are actively involved in committees and associations that are continually developing industry standards for construction and renovation, including the CSA’s HVAC Standard, and the Catastrophic Events section of CSA Z8000 – Canadian Healthcare Facilities. On the technology front, our Angus Connect division is focused technology, including smart buildings technology, and is a leader in providing technology strategy and implementation in healthcare facilities.

To learn more contact:

Kevin O’NeillP.Eng., LEED® AP
Commercial Director

Low and zero carbon energy presents a substantial opportunity for the world. It will deliver significant benefits to the human health, well-being and prosperity, while improving the environment and sustainability of our planet.

The promise of harnessing emission-free energy is an engineering and economic opportunity that is hard to pass on. While eliminating carbon emissions has its health benefits to humans as we reduce air pollution and improve air quality in cities, the transformation to renewable and emission-free energy will help achieve a truly sustainable energy future for the world. This zero carbon energy revolution is coming. It will deliver jobs and reduce the impact of global warming on a wide variety of other important aspects of life. A Low Carbon Energy Transformation is a key component for an effective strategy to reduce greenhouse gases and boost energy security.

The Issue: Climate Crisis

Climate change took centre stage in 2019 as advocates around the world organized events and demanded government action to address the climate crisis. In 2018, the Intergovernmental Panel on Climate Change (IPCC) recommended to the United Nations that the world limit global warming to 1.5 °C (2.7 °F) above pre-industrial levels in order to avoid adverse effects on both humans and the environment. This target is possible, but would require the world reaching zero carbon emissions by the year 2050, as well as fast-tracked and extensive changes in all aspects of society.

Looking to the future, the global population will reach 10 billion by 2050, according to the World Bank. In parallel, the world’s demand for raw materials could double by 2060, according to the Organization for Economic Co-operation and Development. These factors, among others, introduce substantial pressure on the path to zero carbon energy. In order for the world to reach its climate targets, the main sources of emissions to be addressed are human activities related to transportation, agriculture, manufacturing, and buildings. For the latter, achieving near-zero/zero carbon emissions involves tackling multiple aspects, such as building construction and retrofitting activities, building envelopes, and building energy systems.

Challenging the Status Quo

Across Canada, one of the primary approaches to building heating is through fossil fuel combustion. Natural gas and fuel oils are burned to produce steam or hot water which are used for heating, or fuel is burned to heat air and sending it directly into buildings. As for cooling, buildings traditionally use refrigeration systems that rely on electricity from the grid, which may/may not use fossil fuel to generate electricity. In addition, when it comes to electric vehicles (EV), most buildings have yet to install EV charging infrastructure.

Reducing building emissions requires a focus on building energy systems, efficiencies, and strategies in order for buildings to achieve true zero carbon emissions. While ASHRAE standards 90.1 and 90.2 address building efficiencies, new smart and innovative building systems for heating and cooling must become mainstream in order to make tangible progress toward a zero carbon world.

Engineering Solutions 

The good news for building emissions is that there is a wide variety of engineering solutions and strategies available to provide emission-free heating and cooling.  Building owners, collaborating with engineering consultants, face the critical task of establishing evaluation criteria for each proposed emission-reduction solution or strategy, in order to determine which is most appropriate under constraints such as budget, time, and performance, and other practical considerations.

Heat Pumps
One solution is heat pump systems that can be used to satisfy both building heating and cooling loads. While heat pumps are typically powered by electricity, it is worth noting that, in Ontario, approximately 90% of electricity comes from low/zero greenhouse gas sources and has one of the lowest annual average emissions factors in Canada (31 g CO2eq/kWh electricity consumed). Heat pump systems commonly have a wide range of capacities. For heating, such systems are capable of providing heating capacities up to 30,000 MBH (8792 kW) per heat pump, and hot water of temperatures as high as 150°F (65.5°C). For large cooling loads, heat pumps have cooling capacities from 250 tons of refrigeration (TR) (879 kW) up to 1800 TR (6330 kW) per heat pump. These capabilities make heat pumps suitable for simultaneous heating and cooling of buildings in the shoulder seasons. 

Heat pump systems are also capable of providing full building heating in winter when they operate in conjunction with an appropriate heat recovery system. For peak heating loads, these heat pump systems can operate side by side with low emission condensing boilers in a low carbon scenario, or coupled with thermal energy storage (TES) systems in a zero carbon scenario. It is worth noting that, for colder climates, supplemental heating may be required to satisfy peak winter loads in order to achieve zero carbon building heating. This may be achieved with other zero carbon heating alternatives. For peak cooling loads, heat pump systems work in conjunction with high efficiency centrifugal peaking chillers or thermal TES systems. Heat pumps that use carbon dioxide as a refrigerant (R744) can provide both heating and cooling emission free, and could be a promising solution if they become mainstream.

Solar Photovoltaic
Regarding on-site electricity generation, low/zero carbon electricity generation can be achieved by using solar photovoltaic (PV) systems coupled with battery storage in a zero-carbon scenario, or by utilizing small-scale low emission natural gas engines for electricity generation, which can also be coupled with battery or thermal storage in a low carbon scenario.

It is important to note that PV system capital costs have been falling dramatically in the past few years, with solar panel efficiencies up to 23%. In addition, battery storage system prices are becoming more competitive. They continue to decrease in cost and are destined to play a significant role in this market.These economic factors will significantly contribute to the zero carbon transformation for reducing building on-site emissions, as they will help to make projects financially viable.

For large-scale integrated applications, such as neighborhood-scale heating/cooling systems or institutional campuses, buildings can utilize an ambient water loop that operates between 50°F and 75°F (10°C and 20°C), or a resilient redundant thermal grid. This system uses an underground pipe network to supply a heat source/sink capability, which is then coupled with individual heat pumps in each building to either draw heat from the loop or inject heat into the loop. One caveat is that this may require retrofits for some buildings in order to accommodate lower water temperatures for heating. These retrofits may involve implementing measures such as re-insulation of the building envelope, high performance glazing, and upgrading the heating and cooling systems in the buildings.

Energy Storage
On-site energy storage systems, such as battery storage or TES, assist both electrical and thermal grids in satisfying peak demand and increasing overall system reliability. Heat recovery is a similar solution that helps achieve zero carbon. These systems work by reclaiming/dispensing thermal energy from/to sources like wastewater, storm water, and open bodies of water.

For building heating and cooling, geo-exchange thermal energy is supplied to or extracted from the earth’s surface. The advantage of geo-exchange is that the earth’s temperature is stable over time; for example, in some regions of the world, soil temperature below the frost line remains a constant 45°F-50°F (7°C - 10°C) year-round. In other words, geo-exchange uses Earth’s outer layers as a rechargeable thermal battery. This strategy works best in specific climates and involves geotechnical, civil works, and landscaping considerations.

Geothermal Energy
Another promising solution is Geothermal Energy (which differs from geo-exchange). It uses thermal energy from deeper layers of the earth (2500 meters+) to provide higher temperature heat that could be used for process heat or to distribute thermal energy for heating on a larger scale.

Small Modular Reactors (SMR)
SMRs can be safely deployed in remote areas and would provide carbon-free electricity up to 600-1200 MWe per unit, in parallel with high-grade process heat (up to 1112°F (600°C) for capacities up 1.5 Billion BTU), or heat that can be used for city-wide heating.

The Challenges Ahead

Implementing any of the above-mentioned solutions carries challenges, the main one being economics. Any zero carbon solution has to deliver a competitive return on investment for cost per unit of energy, total capital cost, operational cost, and marginal cost for system reliability for mission-critical applications. These emission-free solutions may, however, offer future economic advantages when compared to traditional methods. 

The advantages become clear when considering economic risk factors such as carbon pricing, cost of depreciation of assets due to regulation, and legislative risk, as well as cost savings of new zero carbon technologies arising from future technological disruption. For example, the heat pump market has been changing rapidly in the past two years (2018-2020), introducing large-scale heat pump systems at lower cost which makes them financially competitive. 

Other challenges to zero carbon energy solutions may prove more problematic; for example, the challenges of business repositioning for some energy stakeholders, such as fossil fuel energy producers, distributors, resellers, and equipment vendors. Repositioning businesses to benefit from the zero carbon transformation can induce substantial resistance to change, perhaps due to accelerated time frames, as well as human capital problems, or due to changing demands for skills in the job market.

Planning and deploying an effective energy strategy, including creating and implementing resilient and adaptive energy roadmaps that can actively respond to changing economic and environmental conditions, is a solid start to a zero carbon energy transition.  

Our highly skilled energy consultants are available to discuss low/zero carbon energy options and the transformation solutions best suited to your needs.
For more information, contact


Summary for Policymakers – IPCC

A Clearer View on Ontario’s Emissions - The Atmospheric Fund,

Deep Lake Water Cooling System - ACCIONA

 Geothermal energy - IRENA 


Mike Hassaballa, MASc., P.Eng.

Creating intelligent, responsive and flexible spaces allows building owners to improve occupant comfort, productivity, health & wellness and security, while also increasing the value of the asset. By leveraging data from connected building automation systems, IoT devices and other applications, we can design ‘smart spaces’ that optimize the built environment – from workplaces to hospitals and more.

Benefits of smart spaces

  • Optimize work flows and processes
  • Realize operational and energy efficiency
  • Improve tenant/occupant experience
  • Increase the value of your property assets

Unlike new construction, where it is easier to design and implement smart building technologies,we wanted to better understand the process and pain points around retrofitting an existing structure into a smart space. HH Angus has launched a Smart Spaces pilot project to explore smart building technologies within our own office environment, with the goal of supporting our clients’ interest in similar initiatives.

The Smart Spaces pilot will evaluate technologies that can benefit our clients in a real-world setting. We are installing sensors in selected conference rooms and volunteered workstations that will anonymously monitor occupancy and environmental conditions, such as temperature and humidity. We’re excited to be collaborating with Argentum Electronics, a Toronto-based start-up that is providing the sensors ( Smart Building IoT Platform).

We are also developing a Smart Spaces dashboard and companion mobile app that will aggregate and display data from the sensors and building systems to provide actionable insights, such as adjusting environmental conditions in the space, improve the meeting room booking process, increasing efficiency of lighting systems, and more.

What’s next? The sensors installation has begun, and when these have all been deployed in our office, we will be sharing our progress - including challenges and successes - throughout the process, so stay tuned for updates!  

In the context of the current COVID-19 pandemic, healthcare facilities are looking more closely at options for safe  and fast conversions/retrofits of hospital infrastructure to increase their numbers of patient beds that can serve as airborne infection isolation rooms, as well as ensuring the safety of their operating rooms for performing surgical procedures on confirmed or suspected COVID-19 patients. Recently, HH Angus’ Nick Stark, Vice President, and Jessica Fullerton, Construction Lead – Infection Prevention and Control at The Ottawa Hospital, presented a webinar organized by the Canadian Healthcare Engineering Society, in which they discussed some of the critical design aspects of isolation rooms in healthcare facilities. Nick is Chair of CSA Z317.2, Special requirements for HVAC systems in healthcare facilities. Jessica is Chair of CSA Z317.13, Infection control during construction, renovation or maintenance of health care facilities.

With recent serious outbreaks such as SARS, MERS and now COVID-19, the design of healthcare facilities should take into consideration how these buildings can better address infectious disease control during pandemic crisis situations such as we are currently experiencing. Isolation rooms are one tool that hospitals can utilize as part of their overall approach to safely dealing with certain types of infectious diseases.

Key takeaways from the webinar and our firm’s experience with building systems serving infectious disease control procedures include:

Isolation Room Types

Isolation rooms are grouped under ‘Special Precautions Rooms’. They are sometimes confused with other types of isolation, such as segregation or seclusion rooms; for the purposes of this communication, the term refers to rooms that provide airborne isolation vs contact precautions.

The three main types of isolation room are:

  1. Airborne Isolation Room (AIR) or Airborne Infection Isolation Room (AIIR) — designed, constructed, and ventilated to limit the spread of airborne micro-organisms from an infected occupant to the surrounding areas of the healthcare facility. AIRs are designed to maintain negative pressurization relative to adjacent areas. The AIR room category also includes exam/treatment rooms, which require anterooms. ERs require an internal washroom, and these are recommended for Ambulatory Care areas.

  2. Protective Environment Room (PER) — designed, constructed, and ventilated to limit introduction of airborne micro-organisms from the surrounding areas to an immuno-compromised or immuno-suppressed occupant. PERs are designed to maintain positive pressurization relative to adjacent areas.

  3. Combination Airborne Isolation and Protective Environment Room (AIR/PER) — designed to protect immunocompromised patients who are also infectious.

Operating Rooms for Infectious Patients

These should be treated like a combination airborne isolation room/protective environment room (AIR/PER), and include operating rooms (OR) for infectious patients, along with the OR anteroom that serves as an airlock for stretchers.

The OR anteroom would be negatively pressurized relative to the both OR and corridor.

The OR air handling unit (AHU) requires 100% outdoor air.  Method of Procedure issues must also be addressed; for example, the movement of sterile supplies, identifying a site for intubation, and transportation of the patient to avoid cross contamination. 

Isolation Room Design Criteria

Key room design factors include high level air separation (7.5 Pa of negative or positive pressure, 12 air changes per hour and directional airflow, with non-aspirating diffusers and low-level exhaust near the head of the patient bed.) Also required: a higher level of airtightness to maintain pressure, and consideration of pressure testing during construction to verify effectiveness.

An important tip: during construction, ensure contractors clearly understand what the room will be used for, why sealing is so critical, and why it is vital that there be no leakage.

Regarding ‘grandfathering’ of existing rooms - these require a risk assessment to identify any deficiencies that must be addressed in order to meet the revised standard. Some common leakage sources include lighting fixtures, conduits, sliding doors and uneven floors.


Isolation rooms are designated as a Type 1 space under CSA HVAC standards, requiring uninterrupted operation for airflow, pressurization, temperature, exhaust systems for AIRs, and supply systems for PERs. AHUs require redundancy with parallel, interconnected systems with automated controls and emergency power.


AIR supply air requires two-stage filtration. PER and combination AIR/PER supply air requires three-stage filtration, with HEPA filters downstream of MERV 8 and MERV 14 filtration. HEPA filters can be AHU mounted, duct mounted or terminal. All require accessible means of testing.  On the exhaust side, AIR and AIR/PER exhaust air is treated as contaminated exhaust, and must comply with CSA Z317.2 requirements.  Additionally, recent design improvements for contaminated exhaust include bag-in/bag-out HEPA filters on the exhaust system, in order to reduce the potential for outdoor wind, building wake zones and surrounding buildings to disperse contaminated air.


Anterooms are now required for all AIRs, per Z8000-18, to offer additional controls against unwanted air movement, and for the donning and removal of PPE, among other considerations. Air flow should be negative relative to the corridor and positive relative to the isolation room. Also required – dedicated exhaust from both patient room and anteroom, with the adjacent washroom connected to the dedicated exhaust.

Studies provide strong evidence supporting the use of anterooms, due to the re-emergence of infectious diseases, such as tuberculosis. The CSA has completed a research study of pressure differentials, which interested readers may benefit from consulting: “Pressure Differential in Health Care Facility Airborne Isolation Rooms”. The study, a comprehensive examination of available literature, is helping to inform CSA standards, as well as zoning for pandemic requirements. For example, one finding is that anterooms provide significantly improved containment of particles at pressure differentials above 2.5 Pa, especially during healthcare provider movement through doors. Other systems proven effective in augmenting traditional cleaning are ultraviolet germicidal irradiation systems (UVGI).

Pandemic Planning and Catastrophic Event Management

Designing for planning and management of pandemic and catastrophic events requires consideration of zoning, and how healthcare facilities can isolate entire areas of a healthcare facility. As well, the facility will need the ability to switch between 100% outdoor air to 100% recirculated air, depending on where contaminants originate.  Negative pressure ‘pods’ for ERs and ICUs are also a design consideration, providing the ability to lock down larger areas of a hospital. 

Outbreak Control Zone

These zones have already been in place in British Columbia for the past 12 years, primarily in inpatient areas and ICUs. To create an isolation pod, a typical 16-bed unit is identified and planned as an outbreak control zone. It is designed as a standard patient care unit, but one that can be self-contained. Within the walls of the unit, allowances have been made for clean and soiled holding areas in order to reduce traffic in and out of the control zone. In addition, the area design should provide for a relatively simple procedure to convert it to negative pressure. Also required are defined space for an anteroom that meets the standards for whole unit isolation with all air being exhausted, as well as pressure monitoring and alarms. In addition, controls must be programmed into the Building Management System at the required isolation unit settings, in order to provide single command implementation. These systems are then commissioned, balanced and demonstrated to the facility as part of the verification process.

Operations and Maintenance

CSA Z8001 Commissioning and CSA Z8002 Operation and Maintenance (O&M) standards both offer useful information for O&M processes. Some design considerations to facilitate O&M are: including accommodations for testing and precautions for those who will need to provide O&M for isolation rooms; accessible locations for safely changing bag-in/bag-out HEPA filters; servicing for ductwork inspection and cleaning (annually for CSA and semi-annually for MOL). 

Of special note:  isolation rooms tend to lose pressure over time. For HVAC performance, this stems from degradation of doors and frames, wall openings for maintenance work that were subsequently not properly sealed, damage to walls, and poor sealing of services penetrating walls above ceilings.

Reactivation, Conversion and Retrofits

During the current COVID-19 pandemic, hospitals are seeking to better protect healthcare workers from getting sick, as well as looking at options for safe and fast reactivation of medical and surgical beds to respond to increased demand, including conversions/retrofits of hospital infrastructure to enable this reactivation.

Other options for some healthcare facilities may involve identifying beds/units that were initially designed to serve as AIRs, but were since repurposed. These would require detailed inspection and testing, along with any attendant servicing to ensure the rooms/units meet all relevant codes and standards for patient and staff safety.  

In identifying potential conversion space, hospitals should look for an existing patient area where access to the area can be controlled to minimize interaction between COVID-19 patients and healthcare staff/other patients. The space should also have the ability to be converted to outside air/exhaust that can enable a slightly negative pressure condition relative to the adjacent space which helps in controlling the spread of infectious germs from patients throughout the area. Alternatively, consider modifying an existing private room(s) with individual ductless units which do not circulate through ductwork into a central HVAC system.

For any AIR, the key is to control airflow to manage all contaminants, whether gases or droplets. The air handling strategy utilized (mixed ventilation, displacement ventilation or other) will depend on the size of the room, layout and other factors.

Because speed of construction and becoming operational is critical, effective collaboration and trust between hospital administrators, engineers, designers and contractors is essential. The entire team has to get these rooms designed, approved, built and operating quickly.  

Guidance Documents

Canadian Standards Authority guidance documents dealing with standards for isolation rooms include:
CSA Z8000 Canadian health care facilities | latest issue 2018

CSA Z317.2 Special requirements for HVAC systems in health care facilities

CSA Z317.1 Plumbing

CSA Z317.13 Infection Control

CSA Z317.12 Cleaning and Disinfection – coming soon

Cancer Care Ontario Position Statement – Hospital isolation practices for hematopoietic stem cell transplantation

CSA Study Executive Summary:
Pressure Differential in Health Care Facility Airborne Isolation Rooms
Advisory Panel members include HH Angus’ Nick Stark and Rita Patel

If you would like to discuss any aspect of the design of your facility’s isolation rooms or plans, please contact:

Nick Stark, P.Eng., CED, LEED® AP, ICD.D
Principal | VP Knowledge Management

Kim Spencer, P.Eng., LEED AP
Principal | Division Director, Health

High Oxygen Demand

Due to the COVID-19 pandemic, the high oxygen demand by ventilators and related equipment can create high flow rate demands on a bulk liquid oxygen system, in excess of flow rates for which they were designed. This situation has been reported overseas where increases in flow have in cases exceeded 1000% of design capacity.

Bulk oxygen systems are owned by the medical gas supplier. They consist of a storage tank, a vaporizer, and a gas pressure regulator station as well as a reserve supply.

Bulk oxygen is stored as a cryogenic liquid at approximately -183°C, and then is vaporized to a gas by use of ambient air vaporizer(s), which uses ambient atmospheric heat. Due to the cold liquid temperature, ice does form on the vaporizer (from condensation of atmospheric humidity onto the cold vaporizer surfaces) irrespective of the outdoor conditions. 

The photo on the left illustrates a partially covered surface of a vaporizer; the photo the right shows a vaporizer fully encapsulated with ice (in the middle of the photo). Both photos were taken at different hospitals in southern Ontario during the week of 30 March 2020, when outdoor temperatures were above freezing.   

As ice build-up increases on the vaporizer, the ice acts as an insulator, thereby reducing the available heat transfer surface area; this reduction in surface area reduces the capacity of the system to deliver gaseous oxygen. Vaporizers are sized to allow for certain accumulation and still supply 100% design flow with some degree of safety but, past this flowrate, ice can incrementally accumulate. 

During periods of unusually high oxygen demand, with reduced heat transfer capacity, this can reduce the production rate of gaseous oxygen and can also cause liquid cryogenic oxygen to be introduced into the distribution pipeline downstream of the gas pressure regulators. When this liquid evaporates in the pipeline, the very large change in volume from a liquid to a gas can create significant pressure fluctuations in the pipeline oxygen pressure. 

Removal of Ice from Vaporizers

At all times, but especially at times of unusually high oxygen demand, it is important to keep vaporizers clear of ice. Contact your bulk supplier who will recommend and oversee specialist cleaning companies to perform this maintenance procedure.

Current High Oxygen Demand During COVID-19

It is recommended that a supplemental management plan during this COVID-19 event be established to monitor ice formation on the vaporizer and for ice removal, and to plan for additional high flow rate demand contingencies: 

  • Discuss with your medical oxygen bulk supplier if the LOX tank is being monitored daily by the supplier; if not, monitor the liquid level gauge at least two to three times a day
  • Discuss with your medical oxygen bulk supplier any necessary requirements to deal with a sudden significant step change in flow demand (e.g. keep clear access to the pad for extra deliveries, be ready to support emergency technical service access, etc.) 
  • Discuss with your medical oxygen bulk supplier how much of the surface area can be covered with ice before the evaporator needs to be cleaned; establish response times from the supplier to have a representative on site when the vaporizer(s) need to be cleaned 
  • Do not attempt to remove ice. Contact your bulk supplier who will recommend and oversee specialist cleaning companies to perform this maintenance procedure 
  • Establish daily monitoring of ice build-up; initiate cleaning response as necessary
  • Maintain the area around the evaporator clear of obstructions to airflow, for approximately 3 m if possible
  • Frequently monitor the medical gas pipeline pressure for significant and unusual pressure fluctuations; this may be indicating liquid gas being injected into the pipeline, meaning inadequate vaporizer performance
  • Locate (where provided) the facility emergency oxygen inlet station on the facility façade and verify the shut-off valve is operational.  While the outdoor air temperature is warming, the amount of moisture in the air is also increasing, which can still pose an ice build-up problem over the next few months.

If you would like to learn more about this topic feel free to reach out to:

Ed Hood, P.Eng.,B.Eng.
Mechanical Technical Leader

Kim Spencer, P.Eng., LEED AP
Principal | Division Director, Health