COVID Preparedness
COVID Preparedness
So your kids are going back to school, your going back to the office. What are the risks.
In short COVID hasn’t disappeared, so there is a risk of catching COVID.
As we get to 80% vaccinated its hoped that less people get seriously ill.
What Can be done?
Big question.
We hear about poor ventilation..
We here about 1 person per 4 square meter…..so your kids have to go back to school…but they cant fit in.
We hear about wearing masks and cleaning our hands
Before we work out what can be done we need to understand what we are dealing with…see later.
Who’s at fault if you catch COVID?
Another big question.
So, you rent an office floor. You want your workers back in the office. For now the NSW Govt are saying that’s OK, but don’t exceed 1 person per 4 square meters….OK you do this.
Someone catches COVID and goes legal. Has the NSW Government indemnified you against a claim? ‘They said 1 person per 4 square meters was OK. Don’t think so. I’m guessing you then try to pass the blame and get your landlord into the legal fray.
So, you own the building and rent it out as on office. You know COVID is out there, but you haven’t got a clue what to do. Your tenant is now suing you because they are claiming your building was an unsafe place and one of their employees has COVID.
So, your all in court…the judge thinks about it…and quickly works out an employee has become ill, has lost income or worse, so there is a valid claim.
The Judge then looks to see who is at fault and who has deep enough pockets to pay for the claim.
Judge to Business owner: What did you do to make your work place a safe place?
Business Owner to Judge: Sir, I followed NSW health guidelines of 1 person per 4 square meters and asked everyone to wear masks. I even asked staffs to not come in if they are unwell.
Judge to Building Owner: What did you do to make your building COVID safe.
Building Owner to Judge: Nothing, what can I do. I relied on my tenant to make sure they made their tenancy a safe place.
Judgement: You are both at fault. Pay up.
The above does not represent legal advice, and indeed may be incorrect and is a scenario only for the purpose of this article.
How could this all be avoided?
Don’t think there is a solution to this legal issue, unless the NSW government pass a law indemnifying both parties and agree to pay the plaintiff…..
What Can be Done?
Unless you stay isolated there is a risk of catching COVID. So, it’s a case of reducing the risk.
?COVID – Reducing Risk
There is a thought process out there of not doing anything. This is based on herd immunity (including 80% + vaccination) and the ‘weak‘, slowly exiting from the population profile.
See above for legal issues….this approach is very costly at best and ethically & morally wrong.
Assuming COVID stays around for ever, then when you become older or one of the ‘weak’, you could be exiting the population profile…
So, the best we can do is minimise the risk.
Possible Hierarchy of Minimisation
1)????Double vaccination
2)????Non-attendance, if not well
3)????Temperature checking prior to circulation
4)????Viral quick test prior to circulation. Possibly done at home.
5)????Keep separated
6)????Wear Masks
7)????Hand washing
8)????Surface cleaning
9)????Grouping of cohorts
10) Ventilation (fresh air increase)
a.????Higher Outside air via mechanical means or via windows
b.????Room flush between occupancies and start/end of day
c.????a or b when CO2 levels exceed set point.
11) Do not let room humidity drop to below 40% Relative humidity levels
12) Effective HEPA filtration. This cleans air and captures to some degree COVID. Some degree means relies on COVID making it to the filters.
13) Reduce time of air in space (time and distance). Examples of this is:
?a.????Supplying air in at one of a room and exhausting at the other results in the air being in the space travelling a long distance, potentially being contaminated, before being exhausted from the room
b.????Supply air into one room and this air transfers into another room before it is exhausted…So if viral load in room 1, room 2 is contaminated.
HVAC Related Items
From items 1 to 13 above, items 10, 11, 12 & 13 come under HVAC umbrella.
What Are We Dealing With?
COVID 19 is a virus.
It enters the body typically via airways (nose & mouth). The virus multiplies and inflames your lungs in the main, with the result of reduced oxygen to your organs, brain etc and in worst case scenarios results in death via heart failure or organ failure.
Evidence is mounting that the SARS-CoV-2 virus, which causes COVID-19, can be spread by very small particles – called aerosols – which are released by an infected person when they cough, sneeze, talk and breathe, alongside larger droplets that are released simultaneously (Tang, et al., 2020) (Wilson, et al., 2020).
Larger droplets are acted upon by gravity, and fall after a period of time; the social distancing measure was developed to ensure contact with these larger droplets is reduced. However, fine aerosols (some of which may contain viral particles) can remain airborne for several hours. There is emerging evidence that shows high rates of infection in poorly ventilated rooms, which suggests that this is a potential transmission route.
Measures to reduce the risk of inhaling these small particles, which may cause infection, are therefore recommended.
ASHRAE Position Document…..
A useful read:
Pathogen dissemination through the air occurs through droplets and aerosols typically generated by coughing, sneezing, shouting, breathing, toilet flushing, some medical procedures, singing, and talking (Bischoff et al. 2013; Yan et al. 2018). The majority of larger emitted droplets are drawn by gravity to land on surfaces within about 3–7 ft (1–2 m) from the source (see Figure below).
General dilution ventilation and pressure differentials do not significantly influence short-range transmission. Conversely, dissemination of smaller infectious aerosols, including droplet nuclei resulting from desiccation, can be affected by airflow patterns in a space in general and airflow patterns surrounding the source in particular. Of special interest are small aerosols (<10 μm), which can stay airborne and infectious for extended periods (several minutes, hours, or days) and thus can travel longer distances and infect secondary hosts who had no contact with the primary host.
(a) Comparative settling times by particle diameter for particles settling in still air (Baron n.d.)
b) theoretical aerobiology of transmission of droplets and small airborne particles produced by an infected patient with an acute infection (courtesy Yuguo Li).
Who Are the Responsible Persons - Design?
Who is responsible for advice for minimising COVID transmissions in buildings?
An interesting question.
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We are dealing with a virus and the spreading of a virus. Clearly this wasn’t covered in Engineering Degree lesson 101.
As I see it, the responsible person is the person who understands COVID and how COVID is spread. An Occupational Hygienists.
To put it another way, a HVAC engineer hasn’t got Professional Indemnity Insurance covering off COVID transmission minimisation design.
An Occupational Hygienist is best placed to undertake a risk assessment for each workplace setting. A Ventilation Risk Assessment is their typical deliverable.
This risk assessment may very likely recommend more fresh air, HEPA filtration and the like…and this is where the HVAC engineer comes into play.
What is a Ventilation Risk Assessment?
The occupational hygienist with a lot of formulas, work out the risk of catching COVID in your particular workspace. Infection Risk Parameter (H) is an end deliverable.
Criteria
The following are typical criteria needed for the assessment
Throwing all this data into the calculations will produce many results including predicted number of infections, predicted hospitalisation rates, predicted death rates.
If a space has poor results the usual parameters to adjust are:
1.????Room air rate of change,
2.????Fresh air rates,
3.????Hepa filtration,
4.????Less occupants,
5.????Mask wearing etc.
HEPA Filtration
Filtering air with HEPA filters removes COVID from the air.
For HEPA filters to be effective they need to ‘see the air’. In a room with little air movement HEPA filter units with small air flows, may not see the room air (cleaning only a small amount of the room). To assist, air movement needs to be encouraged. This can be via mechanical ventilation, air conditioning, room fans, window operation (assumes air movement via wind or temperature gradient occurs).
Question: Who removes the HEPA filters when Dirty/containing COVID. Clearly this is a risk and specialised persons, and techniques will need to be considered and incorporated into maintenance budgets.
Who sizes the HEPA Filters?
An emerging trend, or the normal now, is to install portable HEPA filter units in a room.
But how may filters?
Basically, the Occupational Hygienists should advise on the number of HEPA filers as part of their risk assessment.
In short, the air flow rate through the device and the filter efficiency is entered into the risk assessment and ‘toggled’ until an acceptable risk in the room is achieved.
Various literature provide RoT’s for selecting HEPA filters, as follows:
Aim for 5 total air changes per hour (ACH) from outdoor air ventilation + portable air cleaner.
Let’s say a room is 100 m2 and 3m high..
Option a) For 30-persons in space at 10 l/s fresh air equates to 300 l/s (outside air), or 3.6 ac/hr
Option b) Many spaces use 7.5 l/s which is 225 l/s (outside air) or 2.7 ac/hr.
So way short of 5 ac/hr RoT.
HEPA filters capture >99.97% of airborne particles. So, the effective clean air is:
Option a) We are 1.4 ac/hr short of RoT. So, with a min 99.97% HEPA filter we need filters that can provide a minimum of 117 l/s.
Option b) We are 2.3 ac/hr short of RoT. So with a min 99.97% HEPA filter we need filters that can provide a minimum of 192 l/s.
As mentioned earlier the room needs to have the air moved around (full mixing) to ensure the HEPA filter units ‘see the air’.
Note: Installing portable HFU’s, you will need to consider; loss of floor space, consideration of room furniture, maintaining code fire egress paths, noise, nuisance air flows. Power supply and cables.
Please remember HFU’s only reduce risk of legionella transmission.
Increasing Fresh Air
This can be simple or difficult.
Options:
1.????As discussed above you could consider HFU’s only to achieve 5 ach/hour. This option satisfies particle removal but does not satisfy legal fresh air requirements and CO2 will build up in an occupied space.
2.????Open Windows: This requires a study based on weather data to predict likely air movement based on incident wind direction and speed, vs window openings. Where windows are at differing heights a study can be undertaken to estimate the air movement due to temperature difference (buoyancy). Its likely room fans will be required.
3.????Increase outside air on your AC systems. This is energy intensive and may overwhelm your AC system, so careful consideration is required. Given risk of COVID, some loss of room conditions may be acceptable.
4.????Install window fans in windows. This is on the assumption that the space was provided with fresh air via operable windows so installing window fans with no filters is code acceptable.
5.????Install fan filter units with filters from roof air intakes.
CO2 Sensors
CO2 sensors are a great method to determine the number of occupants in a space.
With low CO2 this is an indication of air quality and in particular fresh air.
We recommend CO2 (along with temperature & humidity) to be monitored in each space.
This provides a record of the fresh air and occupancy in a space which could be useful for any future legal action and for taking remedial action to improve air quality, such as:
1.????Automatically starting in room HFU’s
2.????Automatically starting window fans
3.????Automatically modulating outside air dampers for more outside air
4.????Warning room occupants, so they can open windows and or temporarily leave the room.
Note: KAE offer a Multi parameter room sensor complete with online dashboard with ability to control room air fans and or Hepa Filter units.
Humidity in a space is important for protection of human air ways. So, knowing when a room RH is <40% is useful.
KAE can facilitate the following services:
1.????HVAC Audit to determine current ventilation rates
2.????HVAC design to achieve minim Air Flow rates
3.????Commissioning documentation for air flow success
4.????Selection of in room or remote HEPA filtration units , with control via CO2 monitoring system
5.????Via our partners undertake a Ventilation Risk Assessment on your building
6.????Review Natural ventilation
7.????Design & Select, local fresh air delivery systems, with control via CO2 monitoring system
8.????Design & install CO2/Indoor air quality Sensors and associated cloud services
?Contact KAE via our web site, or email?[email protected]