I just built a Corsi-Rosenthal Box. You might be thinking “what?” Well, it’s a simple and inexpensive DIY air filtering device that helps remove airborne viruses, wildfire pollution, pollen, dust, etc. from indoor air. Of particular note: the filters used are good enough to remove COVID-19 aerosols from contaminated air. Also, it’s incredibly easy to build and inexpensive. My Corsi-Rosenthal Box took less than an hour to make using the readily available supplies shown above. And it cost just $94 plus a dollar or two for duct tape.
That compares favorably with the $230 sleek Coway Air Purifier, shown below, that I purchased at the start of the COVID-19 pandemic. Especially since the latter is rated at ~250 cubic feet per minute (CFM) while mine provides ~350 CFM.
My air filter is 40% of the price of the Coway yet provides 40% more ventilation!
To be fair, mine is larger — and uglier. Here it is!
Even though I’d never made one before the air cleaner took less than an hour to put together. If I did it again, I think I could build one in less than 30 minutes.
Materials, tools, and basic construction
All the materials I used are shown above. Here’s the list:
- One 4-pack of 3M Filtrete 20x20x1 furnace air filters [$61.20].
- A Lasko 20″ box fan plus the fan’s shipping box [$32.75].
- About 25 feet of 2″ duct tape.
The only tools I needed were a Swiss army knife, scissors, a pencil, and a loop of string. (Oh, and a thumbtack.)
Because there are already good resources available for choosing components and building a Corsi-Rosenthal Box, I’m not going to replicate them here. Instead, here’s what I found most helpful:
- Could a Janky, Jury-Rigged Air Purifier Help Fight Covid-19? — An early Wired article that motivated Jim Rosenthal to explore low-cost ways to improve indoor air quality and reduce exposure to Covid-19.
- A Variation on the “Box Fan with MERV 13 Filter” Air Cleaner — Jim Rosenthal’s “filter box” improvement on the original air cleaner design (which had a single filter).
- An important third improvement on the original design: adding a fan shroud.
- Corsi-Rosenthal Cube — A great resource on building a Corsi-Rosenthal Box/Cube, with lots of helpful links and videos at the end.
- DIY box fan air filters – Corsi-Rosenthal box — Another great resource for DIY builders.
These resources cover everything you need to know to build inexpensive and effective air cleaners, plus a little interesting history of how they came to be.
Tips on building a Corsi-Rosenthal Box
While building my box I learned some little details that aren’t covered in the core resources above. None of them are vital, but they might help you. Here they are:
Making the box as square as possible
How should the four filters be duct-taped together? See the picture above, which shows the seam arrangement I used to create a square shape. I found that 2″ duct tape worked well for the entire project.
You probably don’t need extra cardboard!
I purchased my fan and filters online, and both got shipped in boxes that are the perfect size to provide the cardboard you need. I used the Lasco fan box for the box base (see below), as well as four pieces needed to seal the corners of the fan mounting and the fan shroud (see next two sections). Very little cardboard was left!
Note that I sealed the bottom of the box along the filter edges and added four additional short strips of duct tape at each corner to reinforce the construction.
Creating four cardboard corner arcs to seal the fan mounting and the fan shroud
Here’s how I marked up the other side of the Lasco fan box to create four corner arcs that sealed the fan mounting and the fan shroud (see next section).
I placed the fan in the center of the cardboard and drew around its edge, creating the outside pencil line as shown below.
After removing the fan, I used a tape measure to find the center of the cardboard and inserted a thumbtack. Then I made a loop of string to draw a circle to cut out for the air exhaust portion of the fan shroud. (Look at the earlier photo of my finished unit to see what the fan shroud looks like.) The right length for the loop will depend on the fan you use. Here are the optimum fan shroud openings (with the 3M Filtrete 1900 filters I used) for two common fans:
- Lasko 20″ box fan: 15″ shroud opening [my fan]
- Utilitech 20″ box fan: 13.5″ shroud opening
So for my Lasco fan, I used a 15″ loop of string to draw a central circle with a 7.5″ radius.
After marking the cardboard I cut the four fan seal corner arcs from the cardboard corners with my Swiss Army knife and duct-taped them in position as shown below.
I then cut out the fan shroud.
All that remains at this point is to place the fan on the top of the box and seal it to the filter edges and the corner cardboard arcs with duct tape. Finally, tape the edges of the fan shroud to the fan.
You’re done! Here, again, is the finished unit.
This Corsi-Rosenthal Box is quiet, even on maximum fan speed, and noticeably more powerful than my commercial Coway unit. I live in a very airtight home — my CO₂ meter shows significantly higher readings when just the two of us are there. So I am happy to have this second unit available when folks visit. Building it was fun and easy. Recommended!
Here are what I think are the two best free easy ways to create graphics for blog posts and presentations if you’re not a graphics wonk. (Note: I am not a graphics wonk.)
I’ve written over five hundred posts on this blog over the last ten years. As they tell you in SEO School, every post has at least one image. I often find an appropriate image on the web, but sometimes I feel inspired to create a graphic that fits better.
In addition, I frequently present at meeting industry events and to clients. Good presentation graphics can really help communicate what I’m trying to say, and strengthen my message.
Are you also “not a graphics wonk”?
I think there are a lot of people like me who have difficulty easily creating even simple graphics. My problem is that I simply don’t use “professional” graphics creation tools enough to be able to reliably memorize the variety of techniques, tools, and processes needed to speedily turn what I visualize into reality.
My graphic designer, whom I happily hire for complicated stuff, can quickly create perspective drawings, remove unwanted photo elements, and tone down someone’s bright clothing. For me, attempting any of these things takes a few hours on the web figuring out how, and making lots of mistakes along the way. The next time (if ever) I want to repeat the process I’ll have likely forgotten how to do it.
Graphic design software like Photoshop and Illustrator — kitchen-sink tools that can do almost anything — are overwhelming for me. What I need is software that:
- Allows me to easily work with and position images and vector graphics.
- Has easy to use, intuitive methods for duplicating, manipulating, aligning, and spacing graphic elements.
- Provides a text tool and a simple palette of basic graphic shapes.
- Includes object grouping to speed up repetitive graphic element duplication.
- Can easily add drop shadows to objects.
- Includes a gallery of my existing work, allowing me to create a new graphic from an old one.
- Can export anything I create as a jpeg.
- Doesn’t include a ton of extra capabilities I’ll never master and therefore never use.
Read the rest of this entry »
When you need professional help, how do you hire the best professional help?
Countless experts — accountants, plumbers, doctors, lawyers, and meeting planners — will take your money in exchange for advice or services. So, when it’s time to minimize your taxes, modernize the bathroom, diagnose that stabbing stomach pain, draft a complex contract, or organize multiple regional conferences — in short, get help with something you can’t do yourself — how do you choose great help?
It isn’t easy. If it was, we wouldn’t hear horror stories about accountants who can’t file a correct tax return, builders who make costly (and hilarious) mistakes, serious cases of medical malpractice, million dollar errors made by attorneys, and mistakes that meeting planners continue to make.
Why it’s hard to hire the best professional help
You need a new kitchen sink. How can you determine whether someone who says they’re a plumber really knows what they’re doing?
There’s a simple reason why it’s tricky to pick great professionals. If you need help, obviously you lack crucial knowledge or experience. So when you seek help, you don’t know if someone who claims to be able to help really can!
Don’t despair! Here are the two essential steps to take to hire the best professional help.
Ask for and check references
Everyone knows that you should ask for references for a professional who’s going to do work for you. Unfortunately, knowing you should do something doesn’t mean you will actually do it. How often do you ask for references from a professional you’re planning to hire? Do you ask a potential builder? An accountant? A doctor? In my experience, I am rarely asked for references.
In addition, many people ask for references but don’t check them! You may think professionals will only give you the names of people who are satisfied with their services. While that’s usually true, talking to references will invariably turn up useful information. For example, you may discover that a plumber does good work but doesn’t finish in a timely fashion. Or an attorney writes competent contracts but his drafts need to be carefully checked to make sure that changes you request are actually incorporated. It’s common to hear information from a reference that immediately makes you decide not to employ the professional.
So getting and checking references before hiring is an essential step if you want to minimize unpleasant surprises. These days, crowd-vetted online sites like Angie’s List and houzz provide a helpful starting place, but you can’t beat talking directly to clients of professionals you’re considering.
See if they’ll say, “I don’t know”
My mother had an unusual set of medical symptoms. Unfortunately, she picked a doctor who was unable to admit that he didn’t know what was wrong with her. Instead, he told her that she had multiple sclerosis, which caused her much emotional upset. Years went by without the relapses or progressions normal to her illness. But she refused to believe that his diagnosis was wrong. Finally I called him up and confronted him, and he admitted that she did not have the disease. Years of suffering could have been avoided if we had ascertained at the outset that he was incapable of admitting that he didn’t have all the answers.
Checking to see if a professional will say they don’t know when they actually don’t is an important hiring step that is rarely performed. Interview the professional and ask them questions about the work you want them to do. Listen carefully to how they respond to your questions. You are looking for them to show that they know the limits of their abilities, and that they are willing to share their limits with you.
If necessary, ask whether they can do something that is a little outside their stated expertise and listen carefully to how they respond. If you hear an unwillingness to admit that they are not able to fulfill your request, you are receiving an important warning. Ignore it at your peril!
Choosing professionals who are aware of and clear and honest about their own limits ensures not only that they can actually do the work you need, but also that they will let you know when they are unequipped to handle any that problems. These are the people you want to work for you.
One more thing
Know your own limitations, and make sure you ask for help when you can’t solve a problem by yourself!
Faithfully execute these two simple steps when choosing professionals and you’ll avoid the common problems that occur when obtaining help with life’s challenges. These must-do steps have made it possible for me to hire the best professional help for years. I hope they help you too.
Here’s a great inexpensive appreciation to provide powerful personal feedback in permanent form to meeting volunteers and staff that complements giving them public appreciations during the event. Event planning committee members and I were the delighted recipients during a recent national peer conference for medical research lab managers.
Simply print copies of your event’s marketing poster, logo, or website main page on white poster stock (see illustration above). Post one copy for each person to receive appreciations, matched with a name card, on noticeboards or tables located in a prominent spot in your venue, and provide some pens nearby. Then, publicize the posters a few times throughout the event and ask attendees to write appreciations for the people posted.
You can see the heart-warming poster I received above. I’ve permanently posted it on my office wall. Every time I look at this poster, I’m reminded of the meeting and the kind plaudits and thanks I received.
At the end of the meeting, remind recipients to pick up their poster before they go!
One more suggestion. Supply cardboard tubes so that recipients can bring their inexpensive appreciation poster safely home. As you can see, mine got a little wrinkled in my suitcase—but I’ll treasure it nevertheless!
According to a widely ballyhooed recent study, event planning is the 6th most stressful job. I have no idea if that’s true, but, looking back on the two-day event I ran last week, I estimate that I had to solve well over a hundred on-the-spot problems that cropped up during the twenty-four hours I was on duty.
If you’re looking for a solution to a problem, there’s a natural temptation to pick the first solution you come up with.
In my experience, this is usually a mistake. An understandable mistake, for sure, but still a mistake. Most of the time, the first solution I come up with is not the best choice, so it’s worth taking a little more time to think before springing into action.
You can reduce the possibility of a poor decision caused by a hasty response by employing The Rule Of Three.
The Rule Of Three
Before deciding on a course of action, come up with three alternatives.
Here are three ways of thinking about The Rule Of Three.
1) Family therapist Virginia Satir encouraged people to have at least three choices. She said:
…to have one choice is no choice;
to have two choices is a dilemma;
and to have three choices offers new possibilities.
–The Satir Model, Virginia Satir et al
2) Jerry Weinberg (who came up with this rule’s name) puts it another way that should get your attention:
If you can’t think of three things that might go wrong with your plans, then there’s something wrong with your thinking.
3) One more formulation: If you don’t have three options for a solution to a problem, you don’t understand it well enough yet, and you might need to explore it more.
Applying The Rule Of Three
It can be hard to apply The Rule Of Three, especially in stressful situations. Sometimes I have a hard time resisting acting on the first idea that pops into my head.
Here are two ways that help me apply The Rule of Three:
1) Get help to come up with more options. When I’m under pressure, asking trusted colleagues to help brainstorm alternatives is a great way for me to widen my problem-solving horizons and avoid missing a great solution. Two (or more) heads are better than one.
2) As with making most changes in your life, practice helps. Commit to apply The Rule Of Three to problems you encounter for three days. Then evaluate the results. How and under what circumstances did The Rule Of Three work for you? Decide whether you want to continue the commitment to maintaining this new approach to problem solving.
Uh oh, only two options here. I’m looking for at least one more. Suggestions?
Photo attribution: Flickr user migueleveryday
Here’s a simple idea, courtesy of edACCESS colleague Bill Campbell, that can come in real handy when you want to live blog a public conference session without devoting most of your time to keeping up with what the speaker or participants are saying.
Crowdsource your event recording! How? Before the session, create a public Google Doc, shorten the weblink to the document, and publish the shortened URL on the Twitter feed for the event and/or on the projection screen in the room before the session starts, together with a request to help out with session notes. Anyone with the web link will be able to log in and help share the work of documenting the session.
Do you ever live blog a public conference session this way? Share your experience in the comments below!
Photo attribution: Flickr user catspyjamasnz