1/ Dealing with an inferno of infectiousness.
We failed to do what was needed to keep this mess from getting out of control. Our situation is horrific and will soon get much worse due to end-of-year holidays + more infectious variant. Vaccine distribution also F grade to date.

2/ All of this means even greater mass casualties (for both those who live and die) in the coming months.

3/ Expect one-half million dead by end of February, a lot more of the following: refrigerated trucks outside of hospitals, hospitals faced with triage, schools that will not re-open, business closures, lost jobs, homeless, and (unfortunately) more.

4/ This makes FOCUSING on layered risk reduction that much more important. Since we have also failed at low-cost testing for families and businesses, let's at least focus on those things that we can do as individuals, businesses, etc.

5/ Universal mask wearing in all indoor spaces other than in own home with immediate family members (masks should be worn if any family member from outside of the household must visit for an essential reason).

6/ Avoid ALL non-essential indoor spaces. I am business-oriented and feel horrible about where we are, but we have put ourselves in such a hopeless place that I see no other way of starving this virus of its host.

7/ If you're able to help restaurants, take-out & tip HUGE. Order BIG, refrigerate for meals over several days. Purchase gift certificates from local businesses for use mos ahead. Continue gym membership for mos w/o attending. Time for $fortunate to step up & invest in community.

8/ Visit only ESSENTIAL indoor spaces outside of your own home, but if at all possible do not visit unless universal mask wearing is required and enforced. See @CorsIAQ pinned tweet for basics of the benefits of universal mask wearing.

9/ Physically distance, even when masks are worn in those ESSENTIAL indoor spaces. While the concentrated plume of aerosol particles from infector is dampened (dispersed) by a mask, close contact behind, to side of, or even in front of (depends on mask) can increase inhaled dose.

10/ For building owners, building managers, and business owners: INCREASE VENTILATION, whether that means opening outdoor air dampers, switching off demand-control ventilation systems, or both, or opening windows/door for buildings without air handling units.

11/ For building owners, building managers, and business owners: Require and enforce mandatory mask wearing by all staff and customers, and establish and enforce protocols for ample (6 ft or greater even w/ masks) physical distancing.

12/ For building owners, building managers, and business owners: De-densify (lower capacity) as much as possible using appropriate queuing of customer entry and allowing as many employees to work from home as is possible.

13/ For building owners, building managers, and business owners: Improve or add engineering controls for far-field (not close contact) inhalation dose. Many will recirculate some indoor air. Improve filtration in mechanical system to MERV-13 (if possible) & MERV-11/12 if not.

14/ Employ portable HEPA air cleaners in small (e.g., less than 1,000 sq. ft w/ 10 ft or less ceiling height). Look for HEPA units without gimmicks and CADR of 300 scfm.

15/ These can be useful for lowering the # of virus-laden particles from air in smaller businesses, e.g., small stores, dental offices. The equivalent increase in ventilation (per hour) = CADR x 60/(A x Z). Here CADR in ft3/min, A = floor area (in ft2), Z = ceiling ht (ft).

16/ Example, a 600 square foot store w/ 10 ft ceiling w/ a portable HEPA air cleaner with CADR = 300 ft3/min is equivalent to an increase in ventilation of 3/hr.

17/ Consider use of upper-room or in-duct ultraviolet germicidal irradiation (UVGI). As with filtration, in-duct UVGI is only useful if there is recirculation of indoor air and not simply distribution of 100% outdoor air in supply ducts.

18/ Note that for UVGI and filtration in mechanical system, effectiveness increases with degree of air recirculation, which means some risk of virus-laden particle dispersal between rooms as well as potential for much lower outdoor air intake in many systems.

19/ This is where portable filtration systems and upper-room UVGI have some advantages.

20/ Still for building owners, building managers, and business owners: Make use of time. Employ staggered work hours over extended work days to de-densify. Allow for worker shifts for outdoor mask breaks.

21/ If infectors leave a building for periods as short as 20 minutes, virus-laden aerosol particle concentrations in indoor air may declines by a factor of 10 to 20 under appropriate ventilation conditions and employment of proper engineering controls.

22/ Be conscious of horrific situation we are in. Remember that you may feel great while being highly infectious. Protect yourself AND those around you. Become more educated on inhaled deposited dose, related factors, and how to "turn knobs" to reduce.

23/ Help to educate others, whether family members, employers, employees, friends, legislators, etc. There is so much great advice about lowering exposure (and dose) of virus-laden aerosol particles. See @linseymarr, @ShellyMBoulder, @jljcolorado, @Don_Milton, more ...

24/ @kprather88, @ProfCharlesHaas, @Wymelenberg, @IAQinGWN, @WBahnfleth, @HuffmanLabDU, @CathNoakes, @gcmorr & a bunch of other great colleagues that I will soon kick myself for forgetting to list

25/ I've also posted a blog on inhaled deposited dose, webinars, & links to important resources from others here: http://www.corsiaq.com . Adding more links soon.

Let's battle this virus every second of every day and starve it of its hosts. Let's save lives. Just do it!