Healthy Buildings: Optimize Health and COVID 19 Ventilation (Best Air purifiers, HEPA Filters)

Harvard Professor Joseph Allen explains how the air in our homes, workplaces, and schools is contributing to disease, poor mental function, and putting us at higher risk for COVID-19. The good news? Solutions can be as simple as opening a window.

Joseph G. Allen, DSc, MPH is Associate Professor of Exposure Assessment Science at the Harvard T.H. Chan School of Public Health and the Director of the Harvard Healthy Buildings Program. See his full bio here:

Interviewer: Kyle Allred, Physician Assistant, Producer / Co-Founder of


0:00 Interview Highlights
0:47 Introducing Prof. Joseph Allen
1:58 Aerosols vs. droplets: is plexiglass helpful against COVID-19?
3:12 Mask on in office building with barriers every 6 feet?
4:11 Why such little recognition of ventilation and filtration for coronavirus?
6:11 Simple strategies to improve ventilation and filtration at home, office, school
7:59 Why “air changes per hour” is so important, healthy buildings, and sick building syndrome
9:44 Air cleaners and best air purifiers for health and COVID 19 prevention
11:43 Clean Air Delivery Rate (CADR) for HEPA filters, Best air purifier reviews
14:10 Optimizing masks: type, fit, data
17:06 Mask fitters and N95 fit testing
18:25 Humidity and coronavirus
20:56 Is airplane travel high risk for COVID 19?
23:42 Portable CO2 monitors
26:13 Ventilation and cognitive performance
28:12 Design changes for better indoor health and performance
29:23 Getting kids back to school for in-person learning
33:22 How schools (and homes) can improve their air
35:07 “BPA free” and chemical “whack a mole”
41:29 Final thoughts from Prof. Allen – humans have become an indoor species

(This video was recorded on January 15, 2021)


Healthy Buildings Website | (Harvard School of Public Health / J. Allen Et al.)

5 Steps to Checking Ventilation in Classrooms |

Air Cleaner Calculator | (Harvard- CU Boulder)

Professor Allen’s Book: Healthy Buildings | (also available on

These toxic chemicals are everywhere — even in your body. And they won’t ever go away | (Joseph Allen – Washington Post)

Inward and outward effectiveness of cloth masks, a surgical mask, and a face shield | (MedRxiv – Linsey C. Marr Et al.)

An inexpensive mask “fitter” |

Prof. Allen on Twitter:


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Video Produced by Kyle Allred



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#COVID19 #SARSCoV2 #HealthyBuildings


  1. Elaine Rogers on December 2, 2021 at 10:34 am

    Thank you!

  2. Chris McKay on December 2, 2021 at 10:34 am

    Same thing Florence Nightingale said about nursing 100 years ago.

  3. 1Sweetsexyflava on December 2, 2021 at 10:35 am

    Ever notice no windows in the hospitals are ever open. I wonder what type of filtration system they have.

  4. Lizzymoore54 on December 2, 2021 at 10:36 am

    Three years ago we had our air conditioner worked on and while the service man was here, he suggested that we put a U.V., light in our air handling unit. This is ( for us ) was and is the best and most cost effective way to purify our whole home. We also have air purifiers with HEPA filters in our bedrooms as well. We’ve chosen to spend our money on this instead of vacations and the like. We are older though and have experienced the world at large before the advent of COVID. We also spend much time outdoors working in the yard and the like to get enough ventilation as well as boost our Vitamin ( hormone ) D.. ☺️🙏👑🌎🌍🌏👑🙏☀️🌬💦

  5. Health and Beauty on December 2, 2021 at 10:36 am

    You may also want to consider indoor plants to clean the air, they can clean some chemicals that air filters may not, just make sure that they are pet safe.

  6. MedCram - Medical Lectures Explained CLEARLY on December 2, 2021 at 10:37 am

    Thanks for watching and subscribing. See all MedCram interviews and COVID-19 updates at our website:

  7. ShayBabé Lyfe on December 2, 2021 at 10:38 am

    Can we get an update on the states that ate using his information to make the schools safer. Thank you!

  8. elizabeth bowman on December 2, 2021 at 10:40 am

    I’ve never understood why we build with windows that do not open, this has always confused me. Many people work in offices that have no windows at all, this is stupid engineering to me.

  9. Raymond Saldana on December 2, 2021 at 10:41 am

    That would make sense if you have clean air. Unfortunately with the fires in California this is not possible. So instead I have a air doctor which has a ultra hepa filter. Cleans air up to .003 microns.

  10. R E on December 2, 2021 at 10:41 am

    Wonderful starting to change the whole system thank you.

  11. xotni on December 2, 2021 at 10:42 am

    I can’t believe I just found this. This is excellent!

  12. Skylar on December 2, 2021 at 10:42 am

    Just amaze that you have over 1 million subscribers. I was there from the start!! Always knew you were great!

  13. beatles65 on December 2, 2021 at 10:43 am

    What about those purifiers you wear around your neck? They seem pretty gimmicky. Thank you for this!

  14. 18 Hands on December 2, 2021 at 10:43 am

    I have always loved the concept of "airing the house out". It’s something I grew up with my mother doing. Now that I live in the desert of Nevada, it is not as frequent since the air quality can be poor with dust and wind, as well as the recent wild fires pushing smoke in our direction. Not to mention, my neighbor smokes hella weed and I dont want the house smelling like it. So it has to be carefully planned.

  15. Arlene Mecinas on December 2, 2021 at 10:47 am

    How about Sir spraying a Lysol to disinfect things u brought inside your space like condo, could it have adverse effect on health in long term use? Thank u

  16. Jessica LT on December 2, 2021 at 10:48 am

    Why aren’t we developing better more comfortable masks?

  17. K Dub on December 2, 2021 at 10:52 am

    Need natural air

  18. B Sweet on December 2, 2021 at 10:52 am

    I simply love this channel, so thank you so much for All the information. Very scientific yet simple to understand 🤓

  19. Margaret Baugh on December 2, 2021 at 10:53 am

    What are some excellent and affordable health air filters you recommend? There are so many out there. Thanks.

  20. R Lee on December 2, 2021 at 10:53 am

    Great videos to inform people,Thank you so much. Hepa filters work I have 3 and now I don’t need to be in a tent inside.
    Oil defusers and scented everything has to Stop, please do what you can to help it’s a huge issue to our immune system!
    👏 Gentlemen your knowledge is priceless, Bravo!

  21. IAMGiftbearer on December 2, 2021 at 10:55 am

    This is very good information about ventilation but the guy should stick to his area of expertise and not comment on rate of transmission in schools because he’s wrong. The Delta variant is a game changer and kids are dropping like flies now and it is in fact spreading in schools. It is not rare. Many schools do not have this high efficiency ventilation that they should have nor are there strict mask, social distancing, nor vaccine requirements, especially in the south. All these problems are established risk factors that we know from CDC and other studies increase the odds of contracting the virus.

  22. Tara miller on December 2, 2021 at 10:55 am

    Hi does having windows open stop mold and slow mold down and kill mold

  23. phil marsh on December 2, 2021 at 10:55 am

    When are we going to be able to get ozone destroying catalyst filters for HVAC systems? Ozone is major problem pollutant.

  24. Delia Ocampo on December 2, 2021 at 10:58 am

    In any season I always open the windows to keep the home not enclosed to let the air get in just some windows and fresh smell not moldy smell 🇸🇽🇺🇸

  25. Ruth Rhoten on December 2, 2021 at 10:59 am

    What about plants growing inside?

  26. tammi popw on December 2, 2021 at 11:00 am

    I live in public housing and I’m seven stories high and we have a air conditioner in the ceiling in our house and it has washable filters what can I do to prevent the spread and better filtration for my house

  27. R Lee on December 2, 2021 at 11:05 am

    Please please please keep up the wonderful work you do, we need you!

  28. Tara miller on December 2, 2021 at 11:06 am

    Do dehumifers and air purfier both kill mold spores and mold also do they both work and are they both worth using

  29. Misty on December 2, 2021 at 11:07 am

    since the builders have stopped everyone from opening windows for air and they said building ventilation (circulate throughout the bldgs.) are better, yeah right! there have been more people getting sick. 1 floor of staff gets sick then 2nd, 3rd…………which ever floor or 2 where staff gets sick then the rest of Bldg. staff will get sick which I’m sure most people have noticed. I remember when we were able to open windows not everyone would get sick. Just saying.

  30. dino0228 on December 2, 2021 at 11:07 am

    How do you safely change a used hepa filter?

  31. June Smith on December 2, 2021 at 11:08 am

    9/19/2021 – Thank you, this was a fantastic and very informative interview. I read allot and watch many holistic online health seminars. A great deal of the information that Professor Allen imparted is corroborated by the leading holistic health professionals who participate in online health seminars. Professor Allen was easy to understand and he provided allot of information in an interesting way without being overly technical. I will look for and watch all of Professor Allen’s YouTubes. The interviewer was also very good.

  32. ShayBabé Lyfe on December 2, 2021 at 11:09 am

    Also about the ionization you mentioned is not good. What about in water? How do we get in touch with this guy?

  33. David MacPhail on December 2, 2021 at 11:09 am

    Finally an intelligent conversation on this important issue. In 1985 when I was a building inspector the Provincial government introduced energy saving measures into the 1985 Building Code in the form of extra insulation and airtight vapour barriers. As someone who had developed severe chemical senstitivies from working with toxic chemicals that brought me together with a doctor who worked with environmentally sensitive patients I was well aware of the importance of both ventilation and active filtration. 

    When the energy saving measures were introduced at the annual building inspectors conference I went up on the stage and said this was a terrible mistake that was going to endanger health and make a lot of people sick. The problem is this initiave was politically driven. So the focus of any metric was solely on energy savings to enable politicians to boast their actions had saved significant energy. There was no interest in considering ancilliary effects let alone looking for any. This experience taught me that the biggest threats to our health are often politically driven. I can’t even begin to imagine how many people suffered from poor ventilaton during COVID lockdowns. Thank you Professor Allen and MedCram

  34. Saamajeeva Karunarathna on December 2, 2021 at 11:11 am

    Great Video Thank you Doctor and thank you MEDCRAM

  35. Carrie Picard on December 2, 2021 at 11:12 am

    I would love him to update his opinion about the transmission of Covid in schools due to the delta variant.

  36. Uba D Tmar on December 2, 2021 at 11:14 am

    Kids needs to play outside boost their immunity. Gardening too helps adults. Stick to the basic, our forefathers knows best that outdoors is good for health.

  37. Maureen Green on December 2, 2021 at 11:16 am

    They should be showing this on the nightly news instead of UFOs, UFOs, UFOs. Thank you both.

  38. Pax2021 on December 2, 2021 at 11:16 am

    Air purifiers ! Hell yeah! The solution against virusses. Also ionisation proved to be a succes! That’s also how they used it in Wuhan. Everyone needs dem in home and at public places.

  39. kerry armstrong on December 2, 2021 at 11:17 am

    i just cracked my windows

  40. glo ing on December 2, 2021 at 11:19 am

    Thanks for this info! Unfortunately with my windows open, my apt gets filled with cigarette smoke, and other odors of neighbors. I open the windows every day, but end up closing them due to bad smells coming into the apt.

    I live in a high rise and can hear the residents talking, and sometimes, coughing and sneezing. So I’ve been shutting my windows due to the odors and who knows what else, entering my apt.

    I have 2 small hepa filter air purifiers I keep on when the windows are closed. (Found them on amazon for less than $50 each, and they noticeably clean the air in the room)

  41. Bob Man on December 2, 2021 at 11:23 am

    Every here acting like opening windows is some big secret.

  42. Christina Hicks on December 2, 2021 at 11:24 am

    I have been in the hospital when windows could be open , and now they can’t. I could breath , and felt much better with fresh air.

  43. Arizona John on December 2, 2021 at 11:25 am

    As a senior I keep my home thermostat down to 62 to 63 degrees round the clock, I rather wear a extra covering, . Plus i run a humidifier most of the day. Will go sit outside on a nice day in winter.

  44. Polka Dot Mailbox on December 2, 2021 at 11:27 am

    Such amazing information. Thank you!

  45. Mirella D'Lima on December 2, 2021 at 11:28 am

    Professor Allen very intelligent and has done a lot to make schools safer against Covid.🙏

  46. V M on December 2, 2021 at 11:29 am

    What about an air scrubber installed in the AC unit?

  47. spacesuitdiver on December 2, 2021 at 11:30 am

    What if the outside air is poor quality? Probably better to use a ventilation damper so it’s filtered?

  48. Blitznstitch2 on December 2, 2021 at 11:31 am

    I bought air filters when this hit. You can attach a filter to a box fan and do the same

  49. Arizona John on December 2, 2021 at 11:31 am

    My house is so cold in the winter, around 62 degrees, the germs dont ever hang around they like warm air. As my family says ,"you could hang meat in here", no flu , no colds. Love it.

  50. Zakiyah Amahad on December 2, 2021 at 11:33 am

    I sleep with a fan on every night,and usually have it running all day. Now getting fans for every room. Thanks doc!

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