Frequently Asked Questions

General Info


Technical Details

Purchase and Usage Outside the United States

General Info

What is Speck?
Speck is an air quality monitor that detects fine particulate matter in your indoor environment and informs you about changes and trends in particle concentration. In select locations, the Speck will also display the outdoor air quality as reported by the nearest regulated, federal PM2.5 station.
What does the Speck measure?
The Speck detects fine particles that are between 0.5 microns and 3.0 microns in size. It then uses this information to estimate PM2.5 levels in the air and reports on these particle concentrations. PM2.5 is directly linked to asthma, cardiovascular disease, arrhythmia and many other adverse health effects.
How is the Speck different from other available air quality sensors?

The Speck measures and reports on particulates in the air, with estimates in both particulate count and weight. In select locations, the Speck will also display the outdoor air quality as reported by the nearest regulated, federal PM2.5 station.

Each Speck is individually calibrated and uses machine learning to maximize accuracy, both of which are major improvements on most other devices.

In addition, the Speck has a full-color screen built-in, designed to sit in your house and show you second-by-second trends in air quality. This is very important because you can then develop an intuition for how your house performs; for example, when the gas heat turns on, when you cook, when you vacuum, etc. How different activities and events affect your air quality will become immediately apparent, and our online guidance then helps you understand how to significantly improve your home air quality.

Another key distinguishing feature of the Speck is related to data ownership—your Speck data belong to you! You have the power to view, analyze and share that information as you see fit. We offer an optional data repository to facilitate data collection, but never assume ownership of your information.

The Speck is Wi-Fi enabled so you can direct all your data reports to an open-source data repository where you can view and interact with your data. You can also download your data for further analysis.

Finally, many companies have announced air quality sensors that will come out over the next two years. We're pledged to buy multiples of every one of them, test them transparently and reproducibly, and publish the results. We are also inviting all air quality sensors to house their data on our open-source repository, where the customer has complete control over their data.

Is Speck especially useful for people with health issues like asthma or can we find a use for everybody too?

It is useful for anyone elderly, anyone with heart conditions, anyone with asthma, and anyone that lives in an urban environment, given how bad air can be and how we can unknowingly have filters that do not work correctly in our home! So, the Speck can be useful for everyone.

In addition, prolonged exposure to polluted air could accelerate the onset of lung disease, heart disease and allergies. Monitoring and controlling your indoor air quality is the first step towards mitigating your risks. Many people neglect their indoor air filters and don't realize how their indoor air quality is affected. With the Speck, you have instant insight to your personal fine particulate pollution exposure.

Is the Speck for indoor use only? What are the limitations for outdoor use?

The Speck is developed mainly for indoor use. While you can put it outdoors—for instance on a covered porch or in a garage—there are many outdoor variables that can impede the Speck's function. For example, it will lose accuracy when humidity levels are very high (e.g. thick fog or during a rainstorm) or if anything obstructs the air intake (e.g. if a spider crawls in).

We will be working on calibrating and designing units that are more effective for outdoor use, and possibly even changing the enclosure for that case. However, that model is still months away.

What are the maintenance and/or calibration procedures needed for the Speck to keep functioning optimally?

Once you receive your Speck, you should not need to adjust the calibration yourself. If there are any firmware/software updates, we will be able push those remotely to your unit via a Wi-Fi connection.

For maintenance, our two main recommendations are:

  • Keep the Speck away from direct sunlight exposure
  • Clean/dust the sensor lens every 2 to 3 months by running compressed air through the air intake at the bottom of the unit

We do not anticipate you will need to do much more outside of these suggestions, but will definitely keep you informed if any changes occur.

How do I get the outdoor air quality reading to show on my Speck screen?

Outdoor air quality readings on your Speck's screen require your Speck to be Wi-Fi configured for data uploads, geolocated, and within 40 kilometers of a regulated, federal PM2.5 station in our database. This feature is currently only available to those who live in the United States and some parts of Canada and Mexico. For a map of all federal stations currently in our database, please see the Public Data page, and uncheck the "Outdoor Specks" and "Indoor Specks" checkboxes.

If you know of an online source for federal PM2.5 data outside the USA, and/or are interested in helping us expand our database of federal data, please email us at


How can I purchase Speck?

You can buy a Speck via credit card in our online store.

If you prefer to pay via check or wire transfer, please contact us at

For bulk purchases (over 10 units) and related discount inquiries, please see our discounts policies and contact us to discuss.

Do you offer discounts or honor tax-exempt purchases?
Where appropriate, yes. Please see our discounts policies and contact us to discuss.
How soon will my Speck ship after placing my order online?
Please refer to the Speck product page in our online store for estimated shipping times.

Technical Details

What are the Speck's technical specifications?
Please see the technical specifications page.
How big is the Speck?
The Speck as a whole is about four inches by three inches; so it's designed to fit most anywhere in the house. The screen/monitor is a 3.2" touch screen. Please see the technical specifications page for more precise measurements and other details.
What is the noise level that Speck generates?
The Speck has a very quiet fan. If you set it on a desk or mount it on a wall, few will notice that it is on. However, if you are very sensitive to sounds, you might notice the noise from the Speck's fan.
What voltage does the Speck require?

The Speck operates at an input voltage of 5V DC (via USB plug). The Speck comes with a USB power adapter for North American power outlets. For users outside of North America, please see the question about using the Speck with a power converter.

The Speck uses a USB micro plug for power, so you can plug it into any wall outlet as long as you have a transformer to USB. We recommend using a USB port or adapter capable of sourcing at least 500mA for maximum reliability. You can also power the Speck by plugging it into a computer; you will need to do this when registering the Speck and configuring it to your wireless network.

What sort of technology does the Speck use?
The Speck utilizes an inexpensive Syhitech DSM501A dust sensor and includes a small fan to increase airflow. We use machine learning to improve accuracy and individually calibrate each unit. The Speck is powered via USB and contains on-board data storage that can hold up to about 2 years worth of data. Each unit is also Wi-Fi enabled, so you can easily upload your data to our online data repository and access your indoor air quality information from anywhere.
What is the Speck's accuracy?
We calibrated the Speck using Met One 2μm particle counters and found a very strong correlation (r2 of 0.9 or higher) during in-home pollution events such as cooking. We also continue to improve our calibration and quality control processes to improve accuracy and precision.
What range of particulate size does the Speck measure?
The Speck is maximally sensitive to 0.5 - 3.0 micron particulates in the air. These are the pollution components most responsible for asthma, arrhythmia, cardiovascular disease, COPD, pulmonary disease and many other quality of life issues. Mold spores and some allergens (e.g. pet dander) also often include this size range, and so the Speck will notice when these peak in a home as well. However, the Speck cannot identify what types of particles are in the air; so, it's an indirect form of detection, but can be useful nevertheless.
Is the Speck capable of measuring anything other than PM2.5?

The Speck records temperature and fine particulate levels only. Particulates can be measured inexpensively and reliably, and, as you know, they are also a very important part of indoor air issues, since they are connected to such a large array of diseases; so, we start here.

There are devices that measure CO or CO2, but do not offer a full picture of air quality; CO is a deadly gas; and CO2 gives you a sense of how stale the air is. VOCs, on the other hand, are important to monitor to gauge air quality, because they are important factors for long-term cancer risk. However, there are no available inexpensive VOC sensors that are reliable long-term. We are still looking, and when we find one we'll certainly make it available.

What's the difference between Raw Signal, Particle Count, and Particle Concentration?

If you view the Speck's data on the web site, or by downloading/exporting as a CSV, you'll see three values all related to particle measurement:

  • Raw Signal or raw_particles
  • Particles Per Liter or particle_count
  • Particle Concentration or particle_concentration

To begin with, the actual value coming from the Speck's dust sensor is the Raw Signal value, which is named raw_particles in the CSV. And that raw_particles name is a little misleading. It's not actually reporting a number of particles, but rather the average time the sensor's detection pin is pulled low in ten-thousandths of a second (per second, averaged over the sampling interval) by particles with a size of roughly 2 microns. This raw value is the input for the algorithm we use to produce the Particles Per Liter value.

The Particles Per Liter value is a count-based concentration--the number of particles per liter of air (ppl). We compute this value from the raw signal value using an algorithm which was tuned to produce results close to what we get from a professional-grade sensor which outputs values in ppl (the one to which we calibrate all Specks). This Particles Per Liter value is named particle_count in the CSV. This value is visible on the Speck's screen when the Speck is in "counts mode" — you'll see a small "c" next to the value when the Speck is in counts mode.

Finally, the Speck also reports a Particle Concentration, which is based on an estimate of particle weight (or, more strictly, mass) where the units are micrograms per cubic meter of air (μg/m3). This value is a bit of a guess. It's a simple linear scalar applied to the count-based concentration (Particles Per Liter) to try to get the Speck to report similar PM2.5 numbers to one of the professional monitors against which we're calibrating. So, like Particles Per Liter, it's also a concentration, but mass-based, not count-based. The important takeaway is that Particle Concentration is a best guess, and won't (can't!) be perfect since the Speck is measuring particles moving across its light sensor which can only give us approximate size but tells us nothing about the mass of the particles. This value is visible on the Speck's screen when the Speck is in "weight mode" — you'll see a small "w" next to the value when the Speck is in weight mode.

What is the meaning of the small letter c or w next to the value on the Speck's screen?

This letter indicates whether the Speck is currently displaying its particle measurement as count-based concentration or a weight-based concentration. The Particles Per Liter value is the count-based concentration, and so the Speck displays a c next to the value. The Particle Concentration value is the weight-based concentration (or, more strictly, mass), and so the Speck displays a w next to the value. You can toggle between the two units by tapping the value on the Speck's screen.

For more information, please see the question about the difference between Raw Signal, Particle Count, and Particle Concentration.

Does the Speck reveal mold spores in the indoor air?
The Speck does not directly measure mold, no. Mold spores can range in size between 2 and 100 microns. The Speck detects well between 0.5 microns and 3 microns, so if you have a mold spore plume, it likely will correlate with heightened Speck readings. Some prior Speck users have detected mold this way. Note, however, the Speck cannot definitively tell you that the particles detected are mold spores; but it can offer an indirect measurement, which could be useful.
Does the Speck measure radon levels?
Unfortunately, no. We haven't yet figured out an inexpensive way to measure radon reliably.
Why doesn't the Speck measure VOC's and other molecules, such as carbon dioxide?
The reason we chose to concentrate on fine particulates first is because of the very strong epidemiological correlation between particulates and numerous health outcomes, from asthma to cardiovascular disease. Equally importantly, we were able to find, incorporate and calibrate low-cost particle sensors that can stay in calibration and provide important information about air quality in the home. VOC's are very important sources of exposure also; however, the inexpensive metal-oxide sensors on the market perform very poorly. They drift, and their calibration expires rapidly. As a result, VOC sensors that are inexpensive can provide unwarranted anxiety through false positives, and also a false sense of security through false negatives. We are working hard to find and develop new technologies for VOC sensing that will perform acceptably; however this is not yet available. Carbon dioxide gives you an indication of the staleness of indoor air and is useful; we are evaluating some CO2 sensors now; however the parts cost is tens of dollars, and so this could add significantly to the price of a low-cost air quality system.
Is the Speck able to distinguish between fine and coarse particulates?
The Speck is most sensitive between 0.5 to 3 microns, but does not distinguish between larger and smaller particulates. A binning counter, such as the Hach Met-One is more suitable for distinguishing between PM2.5 and PM10.
Does the Speck detect specifics such as cigarette smoke?
The Speck measures fine particles in the air, from roughly 0.5 microns to 3 microns in size. So, it would detect emissions from cigarette smoke, yes. However, it wouldn't be able to identify what the specific particles or sources are.
Does the Speck require constant Wi-Fi to function?

No, it does not. The Speck has enough memory on-board for nearly 2 years of measurements. Once you do connect it to Wi-Fi and register it with, it will report any saved data samples up to your account. However, you could also use it as an entirely standalone device; the Speck screen makes that very effective, since you will see instant air pollution values as well as historical trends right on the screen!

Even if you choose not to register your Speck to upload its data to, you should still connect it to a Wi-Fi network, if possible. The Speck uses its Wi-Fi connection to correct its internal clock and download firmware updates.

What types of wireless encryption does the Speck support?
The Speck supports open wireless networks (no encryption), WEP, WPA, and WPA2 Personal. The Speck can use either the 802.11b or 802.11g wireless protocol (2.4 GHz). It does not support 802.11n.
Is it possible to download data directly from the Speck to my computer?

Yes! Your data is exactly that—your data. Our Speck Chrome app provides a way to download data directly from the Speck to a computer, saving it to a CSV file. We provide this capability for users who choose not to configure their Speck to upload to our data repository. Alternatively, the Chrome app is open source, so users with programming knowledge are free to write their own tools to download the data if they wish.

How do I interpret the timestamp value in the CSV I downloaded from the Speck or

Regardless of whether you download data directly from the Speck using our Speck Chrome app, or export the data from the web site, the data will be saved as a CSV file. The first field in the CSV file is the timestamp for when each data sample was recorded. It will either be named sample_timestamp_unix_time_secs or EpochTime, but in both cases simply represents the number of seconds that have elapsed since 00:00:00 Coordinated Universal Time (UTC) on Thursday, 1 January 1970, not counting leap seconds. This system for representing time is also commonly known as Unix Time, POSIX Time, or Epoch Time. For the Speck data files, the timestamp value will typically be an integer, but, in general, it can have a decimal component to represent fractional seconds (thus, when using it in code, you should treat it as a double, not an integer).

We use Unix Time for the timestamp because it's a convenient way to store time, easy to convert, and widely supported by programming languages. For example, in JavaScript, you can convert a Unix Time timestamp of 1442470597 to a Date object like this (you multiply by 1000 since the Date constructor expects milliseconds):

var date = new Date(1000 * 1442470597)

And then, printing it out with date.toString() would return:

Thu Sep 17 2015 02:16:37 GMT-0400 (EDT)

For users using Excel, it takes slightly manual conversion, but it's still easy. For example, if there's a Unix Time value in cell A2, then this formula will convert to an Excel date:

My Speck reading is stuck at 0. What do I do?

This behavior sounds like the internal clock battery has gone dead, and this causes the software on the Speck to report abnormally and stay at 0. You can fix this problem can by replacing the 1225-size coin battery using these instructions.

Purchase and Usage Outside the United States

Do you ship to countries outside the U.S.?
Yes! Shipping costs are calculated during checkout. Please be aware that orders shipped outside of the United States may be subject to duties and taxes imposed by the destination country. The Speck price does not include duty or tax.
Would the Speck function properly with a power converter outside the U.S.?
Yes, your Speck should work fine outside the USA. You can either use a personal USB power supply, or plug the Speck's power adapter into a voltage converter. The power adapter which comes with the Speck has a North American style plug, and can accept an input voltage of AC 110-240V.
Will I be able to register the Speck and connect to Wi-Fi in a location outside the U.S.?
Yes, you shouldn't have any issues with using our software outside the U.S. As long as you have Internet access, you should be able to set up a account, register your Speck, and connect it to Wi-Fi so that you can view your data from anywhere.
Does the "air quality for your location" feature of the Public Data page on show data for countries other than the U.S.?

Sorry, currently, no. Although you can see public Specks from anywhere in the world on the Public Data page's map, at this time the search for nearby regulated air quality monitors only draws from our database of federal monitors within the U.S. (and a handful in Canada and Mexico). Thus, the search feature won't return air quality data for most locations outside the U.S.

However, if you know of a good source for air quality data from another country, please email us at and let us know. We would certainly love to expand our database to include other countries!