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Formaldehyde Sensing for Indoor air-pollution

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by Sara | December 13, 2011 23:25 | 3,855 views | 11 comments 13 Dec 23:25

Research Questions: 1. Are their digital sensors we could attached to roomba that would be able to detect indoor formaldehyde pollution? 2. Are their known methods to remediate indoor formaldehyde?

  1. Are their digital sensors we could attached to roomba that would be able to detect indoor formaldehyde pollution?

Possible sensors:

http://www.synkera.com/pdf/Synkera_TechProfile_HCHO.pdf Dection range: crossreactivity: speed of sensor: recovery time: able to use directly with arduino:

http://www.dart-sensors.com/pages/formaldehyde.php Dection range: crossreactivity: speed of sensor: recovery time: able to use directly with arduino:

http://www.aliexpress.com/fm-store/908964/211259419-500406376/wholesale-MQ-138-MQ138-formaldehyde-gas-sensor-probe-sensor-probe-formaldehyde-gas-detection-module-free-shipping.html Dection range: crossreactivity: speed of sensor: recovery time: able to use directly with arduino:

Bibliography for Formaldehyde and indoor air pollution:

From EPA:

Formaldehyde is an important chemical used widely by industry to manufacture building materials and numerous household products. It is also a by-product of combustion and certain other natural processes. Thus, it may be present in substantial concentrations both indoors and outdoors.

Sources of formaldehyde in the home include building materials, smoking, household products, and the use of un-vented, fuel-burning appliances, like gas stoves or kerosene space heaters. Formaldehyde, by itself or in combination with other chemicals, serves a number of purposes in manufactured products. For example, it is used to add permanent-press qualities to clothing and draperies, as a component of glues and adhesives, and as a preservative in some paints and coating products.

TSCA Assistance Line For further information on formaldehyde and consumer products, call the EPA Toxic Substance Control Act (TSCA) Assistance Line (202) 554-1404. In homes, the most significant sources of formaldehyde are likely to be pressed wood products made using adhesives that contain urea-formaldehyde (UF) resins. Pressed wood products made for indoor use include: particleboard (used as sub-flooring and shelving and in cabinetry and furniture); hardwood plywood paneling (used for decorative wall covering and used in cabinets and furniture); and medium density fiberboard (used for drawer fronts, cabinets, and furniture tops). Medium density fiberboard contains a higher resin-to-wood ratio than any other UF pressed wood product and is generally recognized as being the highest formaldehyde-emitting pressed wood product.

Other pressed wood products, such as softwood plywood and flake or oriented strand board, are produced for exterior construction use and contain the dark, or red/black-colored phenol-formaldehyde (PF) resin. Although formaldehyde is present in both types of resins, pressed woods that contain PF resin generally emit formaldehyde at considerably lower rates than those containing UF resin.

http://www.epa.gov/iaq/formalde.html

http://www.epa.gov/iaq/pubs/hpguide.html#formaldehyde

From: http://fcs.tamu.edu/housing/healthy_homes/indoor_air_quality/formaldehyde/formaldehyde.php

What Affects Formaldehyde Levels? Formaldehyde levels in the indoor air depend mainly on what is releasing the formaldehyde (the source), and the temperature, humidity, and air exchange rate (the amount of outdoor air entering or leaving the indoor area). Increasing the flow of outdoor air to the inside decreases the formaldehyde levels. Decreasing this flow of outdoor air by sealing the residence or office increases the formaldehyde level in the indoor air.

As temperature rises, more formaldehyde comes off the product. The reverse is also true—less formaldehyde comes off at lower temperatures. Humidity also affects the release of formaldehyde from the product. As humidity rises, more formaldehyde is released.

The formaldehyde levels in a residence change with the season and from day-to-day and day-to-night. Levels may be high on a hot, humid day and low on a cool, dry day. Understanding these factors is important when you consider measuring the levels of formaldehyde.

Only trained professionals should measure formaldehyde because they know how to measure accurately and interpret the results. As mentioned earlier, many factors can affect the level of formaldehyde on a given day in a home. That is why a professional is best suited to make an accurate measurement of the levels if a measurement is required.

Formaldehyde is normally present at low levels, usually less than 0.06 ppm (parts per million), in both outdoor and indoor air. Average concentrations in older homes without urea formaldehyde foam insulation (UFFI), are generally well below 0.1 ppm. In homes with significant amounts of new pressed wood products, levels can be greater than 0.3 ppm.

Information on FEMA trailers with Formaldehyde pollution: http://www.fema.gov/media/archives/2008/021408.shtm

  1. Could we help people remediate formaldehyde pollution in their homes?

http://www.sciencedaily.com/releases/2011/06/110623174134.htm

http://hortsci.ashspublications.org/content/45/10/1489.abstract

http://www.sciencedaily.com/releases/2009/02/090217141419.htm



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11 Comments

http://www.dart-sensors.com/pages/formaldehyde.php Dection range: "TBD" ppm Crossreactivity: CO 1% H2 0.1% SO2 12% CI2 -3% Ethanol, methanol 50% Phenol 7%

speed of sensor: Response Time (T90) <30 units:s recovery time: Repeatability TBD unit: % of signal able to use directly with arduino:



It seems synkera's sensor has 10 minute response time and 10 minute refreshing time at 0.25 ppm HCHO. According to the graph it starts to detect HCHO after 10 min. then the sensor works well until 20 min, and then the sensitivity drops out quickly. The sensor begins to sense it again after 10 min (refresh time).


http://www.synkera.com/pdf/Synkera_TechProfile_HCHO.pdf Dection range:targeted, <0.25 ppm achieved crossreactivity: Selectivity of HCHO detection versus benzene, CO, H2O sufficient to prevent false alarm targeted, 50 pm CO response is smaller than 0.75 ppm HCHO. speed of sensor:about one minute to the peak.
recovery time:20 minutes able to use directly with arduino:Yes


MQ-138

1.Applicable gas: Alcohols, benzene, aldehydes, ketones, esters and other volatile organic compounds 2.Detection range: 5-5000ppm formadehyde 3.Characteristics of gas: 50ppm formaldehyde 4.Sensitivity: R in air / Rin typical gas ≥ 3 5.Sensing Resistance: 1KΩ to 20KΩ in 50ppm formaldehyde 6.Response Time: ≤30s(70% Response) 7.Recovery time: ≤60s(70% Response) 8.Heat resistance: 31Ω ± 3Ω 9.Heating current: ≤ 180mA 10.Heating voltage: 5.0V ± 0.2V 11.Heating power: ≤900mW 12.Measuring voltage: ≤24V 13.Working conditions: Ambient temperature: -10 - +50 Humidity: ≤ 95% RH Environmental oxygen content: 21% 14.Storage conditions: Temperature: -20 - +70 Humidity: ≤70% RH


MQ-138

1.Applicable gas: Alcohols, benzene, aldehydes, ketones, esters and other volatile organic compounds 2.Detection range: 5-5000ppm formadehyde 3.Characteristics of gas: 50ppm formaldehyde 4.Sensitivity: R in air / Rin typical gas ≥ 3 5.Sensing Resistance: 1KΩ to 20KΩ in 50ppm formaldehyde 6.Response Time: ≤30s(70% Response) 7.Recovery time: ≤60s(70% Response) 8.Heat resistance: 31Ω ± 3Ω 9.Heating current: ≤ 180mA 10.Heating voltage: 5.0V ± 0.2V 11.Heating power: ≤900mW 12.Measuring voltage: ≤24V 13.Working conditions: Ambient temperature: -10 - +50 Humidity: ≤ 95% RH Environmental oxygen content: 21% 14.Storage conditions: Temperature: -20 - +70 Humidity: ≤70% RH


http://www.gassensor.ru/data/files/pdf/Dart-sensor/Formaldehyde-11mm.pdf

Alternative data sheet for dart sensor

Dection range: 0-10 ppm or 0-25 ppm Crossreactivity: Ethanol and Methanol Speed of sensor: 15 seconds at 20º recovery time: ?


Byeongwon Idea--can we use formaldehyde and a cheap ethanol sensor can we control for ethanol/methanol?


I found a cheap alcohol sensor. Alcohol is mainly made up of Ethanol and Methanol.

http://www.sparkfun.com/products/8880

This sensor is very sensitive to alcohol.

And I think that 11mm Formaldehyde is good as a Formaldehyde sensor.

We can use MQ-138 as an alcohol sensor. But as your post above, the sensor also may detect Formaldehyde.

So my suggestion is that we take tests and make codes about that by using three sensors to find a decent result about Formaldehyde.

Arduino can use 6 analogue inputs at the same time :)

At the very beginning, we need the sensors, and then let's go to Home Depot.


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