Using intelligent ventilation and reduce the risk of infection
See the world each country and region to get rid of the new champions league after the outbreak of the "new normal" is a meaningful thing.Employees will not return to the office and work in an office all day?Will appear on the flexible working hours and mixed office (family + office) of the new requirements?Either way, the arrangement of the safety of the indoor environment, to prevent Covid - 19 about the dangers of microorganisms, such as significant new organization needs responsibility.
In the following paragraphs, experts from visa (Finland) in indoor environment, Anu Katka ventilation system was introduced in detail in the future will be in protection office and other people in the workplace from the role of microbial threats.She also explains why reliable measuring carbon dioxide is crucial, because it is an ideal measure effective ventilation.
Bring the experience and lessons of COVID - 19
COVID - 19 is caused by SARS - CoV - 2 virus, infection can spread the virus in two ways.First of all, the virus can survive for several weeks on surfaces (1), especially in the lower (2) at room temperature.As a result,当人们接触被感染的表面并将病毒传递到他们的口、鼻或眼睛时，就有可能发生污染物传播。其次，当感染者咳嗽、打喷嚏、说话或呼吸时，病毒可以通过微小液体颗粒从感染者的口或鼻向外传播。这些液体颗粒大小不一，可以是较大的呼吸道飞沫，也可以是直径小于 5 微米的较小气溶胶。
According to the world health organization (WHO), in a specific environment, especially in the interior, crowded and insufficient ventilation space, such as restaurants, gymnasium, night club, office and/or place of worship, infected people in a long time, these Spaces with others coexistence aerosol transmission is likely to occur.(3)
The lancet recently in a paperSupport the SARS - CoV - 2 main assumption that spreads through the air, the paper puts forward the support the spread of SARS - CoV - 2 air ten scientific reason.(4)
By understanding mode of transmission, the government has been able to formulate appropriate policies, wearing masks, maintain social distance, wash your hands often and surface disinfection measures to fight against the spread of the virus.It is important that the government also realized the indoor environment is the threat of higher, it is recommended that people actively carry out outdoor activities, and strengthen ventilation.
In November 2020, the British government released a video (5),Emphasized the ventilationTo reduce Covid - 19 the importance of communication.They said in a note: "research has shown that stay in room fresh air particulate matter can be more than 70% lower risk of infection".
In January 2021, hundreds of Canadian experts, doctors, scientists, occupational health and safety experts, engineers and nursing professionals) to the Canadian prime minister wroteAn open letter(6), urging him to "update COVID - 19 guidelines and workplace rules and regulations at the provincial level and content of mass communication, let people aware of COVID - 19 through inhalation of aerosol transmission of the scientific principles."Letter of a main advice is: "suggest that the deployment of carbon dioxide (CO2) monitor to indicate there may be insufficient ventilation situation, in order to reduce the spread of the virus, the sharing of indoor air in a big range of risks.During the outbreak of tuberculosis (TB), up from 1000 PPM of CO2 concentration significantly increased the risk of infection.To improve the structure of the ventilation, keep the CO2 concentration in the 600 parts per million to prevent outbreaks."
The importance of particle size
The WHO said the infection before the onset of symptoms seemed to be contagious.In addition, some infected people have no symptoms, so such an environment, in the office can reasonably assume that the main threat to not only people with severe symptoms such as coughing and sneezing, and from has not realized that he had those infections.These people are more likely to be exhaled diameter less than 5 micron virus aerosol, these particles are not restricted by social distance.These small aerosol particles in the cigarette smoke with the size of the roughly, as is known to all, they are not easy sedimentation, and can be widely spread in poorly ventilated Spaces.
Recently published in the lancet, a paper (7) is introduced for patients with all kinds of respiratory infectious diseases and coughed aerosol breath gas study, in terms of aerosol particle size distribution (mainly small particles (< 5 microns) pathogens), these studies show a striking similarity.These particles can immediately be inhaled, and in most indoor conditions can be retained indefinitely in the air, except through the air ventilation dilution or cleared.
Humidity can also affect the spread of aerosols, because of low humidity will cause aerosol lighter, thus better able to stay in the air.In addition it has been proved that the humidity can affect susceptibility to virus, because exposure to dry air will weaken the host defense ability against influenza virus infection, reduce tissue repair ability, leading to cell decomposition.(8)
Risk mitigation measures
Traditional health and safety risk assessment can be deal with slip and stumble, heavy, repetitive damage, fall, pressure, electric shock, fire danger and work alone, but not to create Covid infection risk environment, organizations also need to include microbial risk assessment.Therefore, it is necessary to determine the potential sources of pathogenic microorganisms and its mode of transmission and means.
Can provide hand sanitizer, and can be used to surface disinfection.To establish procedures to reduce the spread of disease, such as screening, maintain social distance and disinfectant spray and other measures.But, even if all these measures taken, an infected person can also quickly large area pollution.As a result,有效的通风至关重要，控制系统需要对每个房间或空间进行准确及时的测量，以便及时做出响应。一些系统可能只是监测废气中的 CO2，但这并不能检测特定空间中通风不良的问题。
Choose the ideal measuring parameters
Building automation/management system (BMS) is one of the main functions of control comfort temperature and optimize the energy consumption, so the temperature is undoubtedly occupy important control parameter in the space.Some systems also measure and control the humidity to maintain the level of 40-60% RH.This is out of consideration for the health and comfort, and to protect the computer system and avoid mold and related problems in buildings.
Temperature measurement is usually not affected by the drift, but traditional humidity sensor may appear drift, soVisa pull HUMICAP ® sensorsMore popular, because they have long-term stability, and is not sensitive to dust and condensation and other interference.These thin film capacitive humidity sensor has been need long-term accurate, reliable, mianweihu humidity measurement of a variety of applications.
Humidity levels may indicate that human activities and poor ventilation.Humidity, however, as the external factors (such as freeze drying or rainy humid environment) and a significant change, and will not change by human breath.
To sum up, the temperature and humidity monitoring plays an important role in the optimization of BMS, but in facilities management needs to consider personnel take up under the condition of man-made pollution and reduce the space,CO2 is an ideal additional parameters automatically through risk control system.
Using carbon dioxide as an effective ventilation index measurement
Men will exhaled carbon dioxide (CO2) in breathing, CO2 accumulation shows that (a) someone inside the room, (b) ventilation is insufficient, therefore, good ventilation system should be able to detect this and automatically apply the correct ventilation rate.System must be run automatically, and must be able to each space for ventilation, every space in order to get ideal ventilation, and not waste energy excessive ventilation or not need ventilation space for ventilation.
In addition to curb the spread of Covid, CO2 and humidity monitoring and other advantages
ASHRAE standard 189.1 green (us) and European standard FprEN demand 16798-3 recommended control ventilation (DCV), while improve the health level of indoor air to reduce energy use.
Under the condition of the building is mainly composed of people, from the perspective of hvac design,CO2 is ideal indicator of indoor air quality.Humidity will be the better parameters, it is useful to at least additional parameters, especially when used to hold artwork, books, wine, historical relics and other buildings or need to protect the building itself.
Typically, CO2 levels in the outdoor air is 250-400 PPM.In contrast, exhaled gas containing about 50000 PPM of CO2, 100 times larger than inhaled high CO2 content in the gas, therefore, if there is no adequate ventilation, when people stay indoors, CO2 levels rise gradually.
Within the building comfort and performance will be affected by CO2 levels.Air exchange good footprint is 350-1000 parts per million, the CO2 content in higher concentration will cause drowsiness, more than 2000 PPM can lead to headaches, sleepiness, low concentration, concentration, heart rate and mild nausea.Exposure to a very high level (from fuel oil/gas burners or the gas leakage) may even lead to suffocation death.
The ANSI/ASHRAE standard 62.1-2019 "acceptable indoor air quality and ventilation requirements" of the various interior space provides Suggestions for minimum ventilation rates.
Several studies have evaluated the effect of CO2 concentration on cognitive function.For example,Allen et al. (2016)(9), and CO2 content as low as "Green +" level, compared to two days (about 540 parts per million (PPM) in CO2 medium (about 945 parts per million (PPM) in one day, a typical participants' cognitive function score was reduced by 15%, the CO2 concentration is about 1400 PPM of one day, the cognitive function score was reduced by 50%.On average, CO2 concentration, every 400 PPM increase cognition of the participants in the typical score will drop 21%.As a result,基于 CO2 测量的 DCV 可以提供远超 DCV 系统本身成本的健康和生产效率改善。
Select the appropriate CO2 transmitter
Continued performance in BMS will depend on the stability of the sensor, hvac system supplier of course prefer to use sensors can "once and for all".Therefore, it is necessary to choose not to need frequent recalibration can avoid the drift of the sensor.However, some sensors can claim by implementing software solutions, assume that the minimum measurement reading is the same as the concentration of CO2, the average outdoor, in order to compensate the drift, which makes the selection process more complicated.The algorithm of the danger is that small error will over time, can lead to very large error in the long run.In order to avoid to the actual need to be calibrated, the software algorithm for sensor does not apply to the space of people continue to use, in addition, building automation system will be in off-peak hours voluntarily reduce fresh air intake, and these sensors can't recognize this situation.In some cases, even in the concrete wall may absorb CO2, thus "cheat" algorithm and cause further inaccurate.
BMS supplier/installation and building owners/facility management personnel may exist between the minor conflicts of interest.For the former, the system must be perfect operation immediately, and keep the performance at least during the warranty period, but in the latter case, the requirement is more long-term.
Good compared with the benefits, the cost of the sensor.Accurate, based on the requirement of control can save a lot of energy, but more importantly, building personnel's health and well-being will be protected, the indoor conditions can improve performance in the workplace.
As a result,Visa pull CARBOCAP ® CO2 sensorIs the ideal solution.This is because they adopt double wavelength NDIR technology, able to work in a variety of environments, and to be able to use internal benchmarks for the calibration.
Visa pull sensor trouble-free operation is not uncommon for up to 15 years.The stability and reliability has been widely recognized.Visa pull sensor still launch in 2011, NASA's curiosity and Mars rover land on Mars in February 2021, perseverance, Mars the car running.
In a word, on the earth, can through intelligent ventilation and reliableThe CO2 measurementTo strengthen disease prevention measures.In addition, good indoor air quality health and well-being of the building personnel have a significant positive impact.
References:
Kampf, g. et al. (2020), "on the surface of the coronavirus in the biological survival duration and biological kill agent inactivated effect of them", Journal of Hospital Infection.
2. Ratnesar - Shumate, s. et al. (2020), "simulated sunlight can quickly destroy The living creatures on The surface of The body surface SARS - CoV - 2 virus", The Journal of Infectious Diseases.
3. The world health organization: https://www.who.int/news-room/q-a-detail/coronavirus-disease-covid-19-how-is-it-transmitted
4. Greenhalgh, t. et al. (2021), "the SARS - CoV - 2 viruses can be transmitted through the air of the top ten scientific evidence", the lancet.https://doi.org/10.1016/S0140-6736 (21), 00869-2
5. The UK department of health and social care (2020), "supporting ventilation is vital for reducing COVID - 19 spread new film", www.gov.uk/government/news/new-film-shows-importance-of-ventilation-to-reduce-spread-of-covid-19#:~:text=Coronavirus%20is%20spread%20through%20the, virus get % 20 transmissions % 20 happen % 20 indoors.
6. Ricochet (2021), "the government must pay attention to COVID - 19 by the fact that aerosol transmission", https://ricochet.media/en/3423/there-is-still-time-to-address-aerosol-transmission-of-covid-19
Fennelly, K.P. (2020), "contagious aerosol particle size effect on infection control", the lancet - breathing epidemiology, book 8, 9, pp. 914-924.
8. Kudo. E. et al. (2019), "the low environment humidity lowers the body's barrier function and innate immunity to influenza infection", "proceedings of the national academy of sciences, 116 (22).
9. Allen J.G. et al (2016), "cognitive function score and carbon dioxide, ventilation of the office staff and exposure in volatile organic compounds associated: controlled exposure to the green and the traditional office environment research", "environmental health perspectives 124:6 CID:https://doi.org/10.1289/ehp.1510037
