Touchstone: Environmental Quality Monitor for Your Home!

The Touchstone is an open hardware and software indoor environmental quality sensor designed by the National Association of REALTORS/CRT Labs. The idea behind the Touchstone was conceived in the summer of 2016, when we at CRT Labs were exploring various types of personal air quality monitors available in the market. We found that most of them were around $150-$200 for one device, costing a lot more in some cases. They used cheap sensors that weren’t accurate, and almost all had a dependency on a combination of a smartphone app and some cloud platform on the internet that it pushes data to. If we want to monitor the environmental quality of the entire home, we would have to spend around $200 for each room and give up privacy for the sake of cloud access to our data.

The Rosetta Home 2.0 platform developed by CRT Labs aims to solve exactly this issue. We developed it with an offline first mentality – no internet required. Cloud connectivity is optional for data backup, large-scale research and more in-depth data analysis. You are not locked into any one cloud provider or a mobile platform. With the addition of the Touchstone, a home’s environmental quality can now be monitored locally, accurately, and at a relatively affordable price.

A Touchstone can measure the local temperature, relative humidity, carbon dioxide concentration, TVOC (total volatile organic compound) concentration, PM2.5 (particulate matter) mass concentration, sound intensity, light intensity and barometric pressure. With advancement in MEMS and CMOS technology, we now have access to sensors that are extremely cheap and have decent accuracy, and more are being available every day. In order to find the right balance between price and performance, several sensors are tested along with higher-end reference sensors that we know are accurate from literature review of other studies. Sample CO2 data from one of our sensor tests is shown in the graph below:

From the graph, we can see that the sensors can vary widely in the readings. Similar tests are being done for other parameters that we measure. We found that some of the sensors that report incorrect values are currently being used in popular air quality monitors in the market today. Our goal is to maintain relatively high accuracy in sensor readings. This allows our Touchstone devices to be used in large-scale research projects that can provide large data-sets of anonymous environmental quality for different types of climate zones and different types of homes across the country. Ultimately, the goal is to yield useful correlations between this hyper-local data and energy use and human activity.

The Touchstone devices wirelessly send data to a receiver that’s also on the same network. For wireless transmission, an FSK radio transceiver running at 915MHz frequency is used. This frequency band is license-free and set as an ISM band for commercial and industrial products. Using a dedicated transceiver as opposed to relying on commonly used protocols that operate in the 2.4GHz bands such as WiFi, ZigBee, Bluetooth and others allows for robust, low-power and long-range wireless operation. The radio modules have a transmission range of over 500 m in open air and over 150-200 m in occupied buildings. Due to their operation in the sub-GHz frequency bands, they have much better obstacle penetration, greater reception and stronger immunity to the ever increasing RF noise in the spectrum. This contributes to superior performance for the specified application of data logging within buildings. Using dedicated radios also eliminates dependencies on internet access (wired or wireless) on every sensor location as well as electric power in some cases where the sensor can run on batteries for several years at a stretch. Currently, the Touchstone runs on a 5V USB power supply, the same one we use for charging our cell phones. There are application-specific versions currently in development that allow for lower power versions of these boards. The Touchstone and other boards in its family can all be made relatively cheaper than their commercial counterparts.

The gateway receiver has the same radio module which constantly monitors all incoming wireless sensor data from around the building and pushes it over USB to the Rosetta Home platform running on a Raspberry Pi. The data can then be aggregated and monitored in real-time locally, and also pushed to the cloud for remote-monitoring and research purposes if necessary.

Currently, we are designing and testing various types of enclosures at a manufacturing facility called mHUB here in Chicago. Here’s a Touchstone prototype in its enclosure and its relative size in the average hand:

This is how the assembled boards looks like without the enclosure:

The assembly of the board is currently done manually at CRT Labs, as we are iterating over the hardware design and as sensor tests yield more data. Over the next few months, the assembly of the boards will be done at mHUB, which has factory-grade equipment using which the production can scale to several hundred units per day. These devices when complete will be used for research studies to be conducted by CRT Labs in Chicago, and later, in various cities around the country in the coming months. The data that comes from this research can give us an insight on how residential and commercial buildings perform across seasons, and how they impact energy usage. Ultimately, this will lead to more energy-efficient, smart and healthier buildings in the near future.

Building Better Air

I recently wrote about our newest project, A Pocket Guide to Cleaner Air, a book that educates those in the commercial real estate market about how to help their office clients pick and care for plants that can help make their indoor air cleaner and their workers more productive and healthier. Today, I’m going to show off one of the steps the National Association of REALTORS® is taking to help make our office environment in Chicago better. Just like the steps that IREM has taken towards the WELL standard, we are hoping that these plants are a start towards thinking about the indoor space we spend our time in every day. That step is a plant wall, installed on the 4th Floor of NAR’s HQ, which aims to clean our air of CO2 and VOCs to help make the IT department a healthier place.

Plant Wall in the IT department at NAR

Plant Wall in the IT department at NAR

We’ve covered a lot of the benefits of putting plants in indoor spaces on posts before, but to reiterate, we spend about 90% of our time indoors, and the EPA estimates that indoor air quality is 5-10x worse than outdoor air quality! At NAR, we can’t just open up our office windows to try to get in some air, so we need to take measures to help make the air that we are circulating (and recirculating) be as fresh as possible, so we enlisted our friends at Plant Parenting here in Chicago to think of a solution to get some of the plants from the NASA Clean Air Study into our office space. We have pretty typical cubicle walls, with paneling that can be taken out and replaced with different materials, so after measuring the paneling, we discovered we could actually fit some trays right into our walls! Howard at Plant Parenting was able to install this wall for us in a morning, including putting in all the plants. We have 4 kinds of air-purifying plants along the wall, which I will describe below with their benefits.

Plant Wall at the National Association of Realtors

There are 4 different plants that purify the air in these trays!

First up we have dracaena warneckii, a plant that cleans benzene, formaldehyde and trichloroethylene. The warneckii is a bushy plant native to tropical Africa, but it can also grow quite tall depending on the variety. We have the bushy warneckii, because they do not weigh much and thus won’t put a ton of strain on our cubicle walls. We also have a second type of dracaena called dracaena marginata, which comes in a variety of colors and shapes. Marginata not only cleans benzene, formaldehyde and toluene, but also is considered one of the best for cleaning xylene and trichloroethylene. These dracaena are native to Madagascar and other islands in the Indian Ocean. Next up is the Money Plant, and while it won’t make you rich, it will clean benzene, formaldehyde, xylene, and toluene. It is native to French Polynesia. It is one of the hardest houseplants to kill, hence its other name, Devil’s Ivy. Finally, we have a tropical plant from New Guinea called Chinese evergreen, which is said to bring good luck to those who grow it! We’re lucky it will be filtering benzene and formaldehyde out of our air. All of these plants will convert CO2 to breathable oxygen for us as well.

Devil's Ivy on our Plant Wall

Devil’s Ivy close up

We’ll be monitoring our indoor air quality using the sensors we’ve been building in the lab, and seeing how all our hard work getting the right plants together pays off. We’ll keep you all posted, and hope that our results inspire you to start putting plants in your own offices. And stay tuned for more info about our Pocket Guide to Cleaner Air!

Coming Soon: A Pocket Guide to Air Purifying Plants

Over the past few months, CRT Labs, along with NAR’s Library and Information Technology staff, have been researching and developing a series of books about indoor air quality and plants you can grow in order to keep your air fresh and clean. The first in this Pocket Guide series is a book specifically aimed for commercial practitioners, and will educate REALTORS® about the best plants to advise their clients to buy for improving the indoor air quality of different office spaces. Further guides will dive into different residential air quality concerns.

NASA Plant Study

In the late 70s and early 80s, NASA began evaluating a variety of plants on their space stations to help clean the air onboard of not only carbon dioxide, but also from gases called volatile organic compounds. These gases, when contained and allowed to circulate in an indoor space, can lead the building’s occupants to contract a variety of illnesses. NASA identified 31 plants in their Clean Air Study as some of the best filters for these contaminants. We single out 10 of these plants due to their high ratings in the Clean Air Study as well as their availability at home and garden centers to focus on in our Pocket Guide. The book examines the best plants that work together to mitigate common indoor air quality issues in commercial spaces, teaches how to take care of these new plants, and includes rich color photographs of each plant discussed. Look for the book coming out in late spring or early summer this year, but until then, enjoy this excerpt from the book! These two paragraphs are from chapter two, titled “Thinking About the Air You Breathe.”

The average person spends around 90% of their time indoors, and the EPA estimates that indoor air quality can be two to five times more polluted than the air outdoors. This rise in indoor pollution is partially due to the fact that office design has shifted towards materials that release volatile organic compounds into the air. Volatile organic compounds, or VOCs, are found in almost all the materials in your buildings, especially in new construction – including the furniture, carpets, paints, cleaning products, and more. Buildings, which are more energy efficient than ever before, have tighter seals and are better constructed, which traps any pollution created indoors, or brought from the outdoors, in the building itself. These factors contribute to these higher levels of VOCs, as well as CO2, in the indoor air. Even while indoor air filtration systems are in use, VOCs can remain and continue to off-gas into the indoor environment.
VOCs, CO2, and other indoor environmental factors all contribute to sick building syndrome, which the National Institutes of Health define as “various nonspecific symptoms that occur in the occupants of a building… [which] increases sickness absenteeism and causes a decrease in productivity of the workers”. The symptoms of sick building syndrome include headache, dizziness, nausea, eye/nose/throat irritations, dry cough, dry/itching skin, difficulty concentrating, fatigue, sensitivity to odors, hoarseness of voice, allergies, cold/flu-like symptoms, asthma, and personality changes. Looking at this list, there’s an overlap in symptoms that are commonly associated with high levels of CO2 and VOCs in the air, meaning that sick building syndrome is likely brought on by these very gases.
The NASA Clean Air Study can be read in full at NASA’s website.