Ventilation, including fume hoods, consumes 40–70% of the full energy used by modern-day laboratories. Energy-conscious fume hood usage—for example, closeup of the door the sash when a hood is unused—can considerably reduce power expenditures as result of ventilation. Prior approaches to promote such behaviors among lab users have actually primarily relied ~ above passive feedback methods. In this work, we developed a low-cost fume hood monitoring machine with energetic feedback come alert laboratory users when a fume hood is left open and also unused. Making use of data gathered by the structure management system, we observed a 75.6% to decrease in the median sash elevation after installation of these “Motion and Sash Height” (MASH) alarms, i m sorry would result in a reduction around equal to 43% of the annual carbon emissions the a common American vehicle, for each fume hood. The MASH alarm presented here reduced energy costs by about $1,159 per year, per hood, in ~ MIT.

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Fume hoods keep the high quality of air in laboratory workspaces while conducting experiments through the potential to release toxic fumes. Hoods also serve together a barrier between rap users and also potential spills, splashes, fires, or explosions entailing hazardous chemistry that might occur during an experiment. This physical defense is noted by the sash, a transparent home window which frequently slides vertically at the former of a hood to permit access. Meanwhile, air top quality in the greater lab space is preserved as hoods constantly pull air inwards (beneath and around the sash), and expel this air the end of the structure through an exhaust system. Removing the big quantities that air drawn through fume hoods in ~ a laboratory subsequently areas a load on the building heating, ventilation, and air conditioning (HVAC) system, forcing the device to readjust to preserve the preferred temperature, humidity, and other variables related to human comfort and also providing a managed environment for experiments. The energy required because that these adjustments easily adds up, consuming 40–70% that the complete energy supplied in modern laboratories1,2,3. Whereby some attempts have actually been make to move towards horizontal sash hoods for energy savings, the research community prefers the ergonomics the a upright sash and vertical sashes contain far better than horizontal sashes at the same face velocity4. This then leaves them greatly unchanged because that the previous 60 years5,6. Some literary works proposes temporary shutdowns of the fume hoods once not in use7, yet there space inherent dangers to users and also building occupants without proper decontamination and communication, both of i m sorry are medium to permanent approaches.

A far better option is to use variable wait volume (VAV) fume hoods, i m sorry account for 67% the hoods in the united States8, exhaust air at a flow rate proportional come the height of their sashes. There have been numerous attempts to alleviate the quantity of power that is wasted by VAV fume hoods by reducing the average height of the sashes of this hoods. A routine at the Massachusetts institute of modern technology (MIT) detailed lab users v monthly feedback on your lab groups’ performance in keeping sashes close up door in your lab spaces, and resulted in a 26% decrease in the median sash height9. In ~ Harvard, “Shut the Sash” sticker labels were put on fume hoods and used in conjunction with automatic sash closers to reduce the HVAC energy consumption by 70%2,10. A examine at UC Davis tested the impacts of similar stickers and found they conserved $1,300 annually, every hood, in energy price savings11. The passive methods used in these researches did not straight encourage user behavioral readjust at the moment of the habits to be changed, however; in contrast, feedback closer with time to the habits or activity to be adjusted has been reported to be an ext effective9,12. Further, a examine from the college of Toronto uncovered that passive approaches had tiny long-term effects on behaviors13.

More recent research at MIT showed that the use of energetic feedback, in the kind of listening alarms, significantly reduces the quantity of power wasted by fume hoods8. In the work, a maker was developed to monitor the sash height of a fume hood and any motion occurring in front of the hood using a webcam and augmented truth (AR) sign attached come the hood. This device was programmed to notify users once they left the hood unattended and neglected come shut the sash. The device reduced wasted power (defined as excess energy consumed together a an outcome of the hood gift open when not in use) by 87–98%. It cost $264 per device and saved labs $358 per hood, top top average, in yearly energy costs. Among the key drawbacks that this device, however, was its cost: in spite of having a payback period of less than one year, the “large” initial investment was hypothesized to possibly prevent labs or facilities departments from investing in this power management solution. In addition, this device required substantial setup procedure and had a relatively large footprint (approximately 10 × 10 × 30 cm). Finally, the AR tags placed on the hood can interfere v lab work, or, alternatively, rap users could interfere v the AR tags, detrimentally impacting the performance of the device. Therefore, this work-related seeks to fill a research void through the advancement and evidence of principle of a smaller, less expensive device with a simplified setup procedure the produces the very same feedback when a hood is open and also not in usage would get rid of these concerns while still supplying the desired energy-saving benefits. This work then looks for to validate energy savings with real-world implementation and results.

In this work, we developed an inexpensive (less than $20) fume hood monitoring device, referred to as the Motion and also Sash height (MASH) alarm, that provides energetic feedback to lab users as soon as fume hoods are left open and also not in use. This an equipment does not keep data, and, in comparison to the use of live handling of a video stream of the fume hood to collection data provided in former work8, that requires only a passive infrared (PIR) motion sensor and also a magnetic reed move (a kind of limit switch) to recognize whether users room present and if the sash has been left open. We placed these MASH alarms on 17 fume hoods (the “test” group), and we monitored these hoods, as well as nine hoods without MASH alarms installed but co-located in rooms the did have actually MASH alarms on other hoods (the “influenced” group), and 19 hoods in rooms without any alarms installed (the “control” group). All of these hoods to be monitored by a pre-existing building management system, which recorded their instantaneous sash heights end time. We uncovered that hoods in the check group showed a 76% typical reduction in sash height contrasted to a reduction of only 10% in the regulate group. Surprisingly, we found that the hoods in the affected group also exhibited a 71% reduction, arguing that far-reaching changes in user habits can be attained also without usage of MASH alarms top top every fume hood within a provided lab (possibly by increasing lab user awareness). The median reduction in sash elevation for the test group of hoods synchronizes to a predicted annual electrical power savings the 3734 kWh (13,442 MJ), heavy steam savings of 70.0 klbs (71,644 MJ), and chilled water savings of 1997 ton-hours (25,283 MJ) per hood with the MASH alarms installed, which is identical to a financial savings the $1159 per year and also a reduction of 2.0 metric loads of CO2 emissions per year. This analysis assumes continuous energy-based energy pricing efficient for MIT in 201814.

We constructed the MASH alarm utilizing an Arduino UNO R3 microcontroller as the main processor. Us attached a magnetic reed switch, a passive infrared (PIR) activity sensor, a piezoelectric buzzer, and also an resulted in the Arduino UNO (Fig. 1). We used the magnetic reed switch to determine if the sash the a hood was open. The reed switch was attached to the side of the frame of the hood, and also a small magnet was attached to the movable sash of the hood and also aligned next to the reed switch such the the circuit would certainly close when the sash was fully shut, and also the circuit would certainly open once the sash was lifted (due to misalignment in between the magnet and also the reed switch). The reed switch habits was identified in both slide (Fig. 2a) and mirrored (Fig. 2b) configurations together a function of sash height; we offered the sliding construction in this study. Come detect if a lab user was current at the hood, we relied ~ above the PIR movement sensor, which might detect any type of movement that occurred directly in former of the hood (we experimentally identified the sensitivity of this ingredient in detail, displayed in Fig. 3). In enhancement to these modules, we included a piezoelectric buzzer and also LED to indicate when the alarm to be active, i.e., once a laboratory user had unnecessarily left the hood open for an extended duration of time while not in use. The enclosure the the alarm was made from a sheet of corrugated plastic (fluted polypropylene) folded right into a 5.5 × 8.4 × 3.2 cm box, and also the enclosure contained the Arduino UNO, PIR activity sensor, buzzer, and LED. This enclosure to be designed through openings come (1) supply power to the Arduino UNO, (2) upgrade the regimen on the Arduino UNO, (3) enable the movement sensor to monitor the surroundings, and also (4) feed the wires to the magnetic reed switch.


The fume hood monitoring device. The an equipment is written of one Arduino UNO R3 microcontroller board with off-the-shelf peripherals (a) connected as presented (b). The assembled machine is encased in a corrugated plastic enclosure (c) and an installed to one next of the fume hood sash (d).


Magnetic reed switch characterization. Based upon ten magnetic reed switches and maintaining a 6 mm clearance in the mirrored case, the hood sash is report to be closed in ~ a separation street of 15.0 mm in the sliding situation (a), and 23.6 mm in the mirrored orientation (b).


PIR activity sensor characterization. 1.2 m (four feet) over the ground and in former of the fume hood, PIR activity sensors produced repeatable results and are perfect for usage in this application. Qualitatively, “high” sensitivity shows that only a tiny movement by a human being user have the right to be sensed (a tiny motion that a finger), if “low” sensitivity suggests that a large movement (waving a hand) is compelled for the sensor to detect motion. The sensor have to be positioned away from typical walking courses to avoid false movement detections.

The MASH alarm repeatedly checks whether the magnetic reed move is open and also if there is motion detected by the PIR activity sensor. This regimen loops indefinitely as long as the an equipment is powered. If the magnetic reed switch has been left open and also there has been no activity detected through the movement sensor for a specified amount of time, the alarm will sound and also the LED will flash. The amount of time until the alarm sound is an adjustable variable in the regime (as described in the Supplementary Information, section S1). We polled a portion of the labs that would be involved in the experiment, and we found that a three-minute hold-up would be satisfactory (i.e., unobtrusive) for most of the labs. More work can be excellent to assess the sports in energy savings as a result of an altering the delay, or the affect of a variable delay dependent top top the kind of lab study being conducted, may be beneficial, and could stand for a helpful collaboration with behavioral scientists; such job-related was not consisted of within the border of this research.

We set up MASH alarms on fume hoods in structure 56 at MIT. The research performed in building 56 drops predominantly under the biology, chemistry, and chemical engineering departments, and also there space a full of 45 change air volume hoods operating in the building. We installed MASH alarms on 17 fume hoods (the “test” group). A 2nd group consisted of 19 hoods that did not receive MASH alarms, were not affiliated with the labs or study groups associated in our test, and also were no in the very same rooms as any of the MASH alarms (the “control” group). Finally, nine hoods were either in the very same room as a MASH alarm, or were used by a laboratory or research group that received some number of MASH alarms in various other rooms in your lab an are (the “influenced” group). Every MASH alarms were set up on September 17, 2018, through the exemption of one MASH alarm that was set up on September 14.

To collection sash elevation data, we retrieved data from KGS Buildings’ Clockworks system. Clockworks is a data aggregator and archival system employed through MIT come collect and also store data from individual buildings’ structure management systems, including chilled water usage, vapor usage, and also fan power, among other data. We supplied data gathered by the sash elevation sensors connected with the fume hoods the we thought about in this study. Through Clockworks, this data was easily accessible in five-minute allude data; we supplied this data to to compare the mean sash heights during the expectancy of the 11 weeks prior to the alarms were mounted (July 1 v September 16, 2018), through the 11 weeks throughout which the alarms were active (September 16 through December 1, 2018) (Figs. 4, 5). We also averaged the five-minute point data to weekly median sash elevation values to assist visualization the the data; a decreased weekly sash elevation indicates the the hoods to be left open up for much less time transparent the week, implying the lab individuals were shutting the sash much more consistently once they left their workspace unattended, and also thereby saving energy15.


Test hoods versus control hoods. This figure shows the typical sash heights the the test and also control groups, as taped every 15 min (lighter fancy lines), overlaid v the weekly median sash heights of both teams (bold). After ~ the installation of the MASH alarms, the sash heights of the manage group remained relatively unchanged, however the test group exhibited a far-ranging drop in typical sash heights. (A worth of 0.07 or below corresponds to a close up door fume hood sash in the KGS Clockworks system).


Test hoods versus affected hoods. This number shows the mean sash heights of the test and influenced teams recorded every 15 min (lighter fancy lines) and also the weekly typical sash heights the both teams (bold). The dashed line shows when the MASH alarms were installed. Despite not having an alarm attached come the fume hood itself, having an alert co-located in the lab brought about the median sash height of the “influenced” hoods to decrease in a comparable manner to the check group. This evidence shows that having actually an alarm near a hood, or having knowledge the the alarms are mounted on other hoods in the lab, can reason lab individuals to operate their hoods in a more energy effective manner. (A value of 0.07 or listed below is thought about closed by the KGS clockworks system).

From the sash height, we can estimate the amount of power consumed by the fume hood based on the area the the sash opening and also the rate at i m sorry the hood pulls air, i.e., the challenge velocity. A calibrated TSI VelociCalc 9535 waiting Velocity Meter was offered by a MIT health and safety representative to measure the face velocity at each fume hood and the results reported to the team. Fume hoods require roughly 1.8 watt per CFM (cubic feet per minute) of air flow that is pulled through the hood and exhausted16. In our experiment, we averaged the values of the sash width, sash height, and face velocity for each team to recognize representative hood features for every of the three groups. We uncovered the representative sash width and also face velocity by averaging the measured worths of the hoods in every of the 3 groups, which at some point provides the quantitative average energy intake on a per-hood bases because that each group of hoods by the commutative residential property of multiplication. To calculate worths for the average sash height before and after environment of the MASH alert in each group, we supplied the Clockworks data. By multiply the typical sash elevation by the mean sash width and face velocity, we calculated the mean CFM the the hoods in each of the three teams (Eq. 1). We found the regulate group to have actually an typical of 250 CFM (0.118 m3/s) before the environment of the MASH alarms, which decreased slightly come an average of 227 CFM (0.107 m3/s) after the alarms were installed in other places in building 56 (Fig. 4). The test group was uncovered to have an median of 313 CFM (0.148 m3/s) prior to the MASH alarms to be installed, which diminished by end 75% come an average of 77 CFM (0.04 m3/s) after the alarms were set up (Fig. 4). The affected group exhibited an median of 362 CFM (0.171 m3/s) before the MASH alarms were installed and an mean of 105 CFM (0.05 m3/s) after ~ the alarms were mounted (Fig. 5). We provided this data to calculate the average energy intake per hood for each group in our examine by multiply the average airflow price (in CFM) by 1.8 W/CFM (Eq. 2). This worth represents the median power draw from a hood in each group over the duration we accumulated the data, in watts. Us used electrical energy units of kWh/yr for less complicated comparison with various other literature. A full year (8760 h) is supplied for the expression of time due to the fact that the fume hoods run continuously unless the hoods, and also their linked ductwork, have actually been decontaminated and the room rebalanced to ensure compelled air readjust rates space maintained, which happens rarely and also typically only as soon as a hood is being permanently decommissioned.

$$ Volumetric;Air;Flow left< CFM ight> = left( sash;height left< extft ight> ight) x left( sash;width left< extft ight> ight) x left( face;velocity left< extft/ extmin ight> ight) $$
$$ Electric;Energy;for ;Fans left< extkWh/year ight> = CFM imes 1.8fracWCFM imes frac1 ; extkW1000 ; extW imes frac8760; exth1; extyear $$

Similarly, for the heating and also cooling loads, we offered the outdoor air temperature and also relative humidity native the TMY3 (Typical Meteorological Year, 3rd collection) dataset because that Boston Logan airport and also assumed the the wait was yielded to the an are at a strict setpoint that 65 °F (18.3 °C) using a dewpoint-based regulate strategy v a 55 °F (12.8 °C) dewpoint and also humidification come 50% loved one humidity (RH). To achieve this, the assorted enthalpy differences in between stages in the waiting handler to be calculated and included together together applicable. This procedure encompasses the sensible addition of half of the complete fan strength (assuming the supply and exhaust pan power space equally split), the initial preheating stage to preheat air come 35 °F (1.7 °C), the cool water coil to cool and dehumidify the airstream come 55 °F (12.8 °C), the reheat stage to heat the air come 65 °F (18.3 °C), and also the humidification phase to humidify air come a 50% RH minimum in ~ 65 °F (18.3 °C). In the process, heating, cooling, and humidifcation are applied only as needed. Because that example, 40 °F (4.4 °C) external air just experiences heating impact when passing end the reheat coil. Likewise, 55 °F (12.8 °C) and 100% RH wait does not obtain or offer up heat to any kind of heat exchangers when passing with the waiting handler. In ~ 65 °F (18.3 °C), the 55 °F (12.8 °C) and 100% RH air would be identical to 70% RH. On a unitary basis, each CFM (0.028 m3/min) each year consumes 296 lbs (302.4 MJ equivalent) of steam and 8.43 ton-hours (106.7 MJ equivalent) of chill water because that the Boston climate under this control strategy.

Our experiment demonstrates the hoods v a MASH alarm installed exhibit a decrease in median sash heights of end 75%. Additionally, the hoods in the influenced group, co-located in labs v MASH alarms present yet without MASH alarms installed, experienced a diminish in mean sash elevation of over 70%. Meanwhile, the median sash height of the regulate group go not change significantly; in the control group, the mean sash height lessened by only 10%. These outcomes are summary in Fig. 6. It have to be provided that the baseline situation was a situation in which the fume hoods already had the customary “Shut the Sash” stickers, but did not have a laboratory manager actively monitoring the sash heights in either the pre or post-installation cases. More laboratory monitoring involvement might be helpful.

Summary of results. Typical sash heights are displayed before and after MASH installation, with error spare based turn off of a 95% trust interval. The mean sash elevation decreased amongst all groups. With the 95% confidence interval, the check group’s median sash height diminished with statistical definition (described in the Supplementary Information, ar S4).

We calculated a 95% percent trust interval top top the mean sash heights before and after installing the MASH alarm throughout the hoods in each team to determine if the typical sash heights adjusted significantly due to the visibility of the alarm (details consisted of in the Supplementary Information, section S4). We discovered that, in ~ a confidence level that 95%, the to decrease in the mean sash height in the control group was no statistically significant, while the distinction in the test team was significant (Fig. 6). The affected group’s diminish in sash elevation was more significant than the of the regulate group, but less 보다 that of the check group. These results show that the presence of a an unified auditory and visual alarm, supplied to carry out real-time feedback, reminded lab users to close up door the hood as soon as not in use, top the lab to use considerably less energy than the would have actually without the MASH alarm.

Fume hoods that were located in the very same room together a MASH alarm had actually a similar, slightly smaller sized decrease in typical sash height. This is likely due to the lab users either hear the alert or otherwise learning that the experiment to be occurring, which resulted in them come consciously (or subconsciously) shot to close your sash once not in use. This confounding variable is a positive repercussion of having at the very least one alarm installed in a laboratory. This effect should motivate research teams to install at least one MASH alarm in their laboratory.

The electrical energy saved in the experimental group (comparing the averages before and after installation of the MASH alarm and extrapolating come a per-annum basis) amounts to 3734 kWh/year every hood. Utilizing data from the U.S. Eco-friendly Protection Agency, this is indistinguishable to 2.6 metric loads of CO2 in carbon emissions, or approximately one third of what the average family members produces in the very same amount of time17,18. Utilizing data particular to the MIT campus, this reduction would certainly be indistinguishable to 2.0 metric loads CO214. Having around one thousands VAV fume hoods in use, MIT would annually save 3734 MWh (13.44 × 106 MJ) that electricity, 70,003 klbs (71.64 × 106 MJ equivalent) that steam, and also 2.0 million ton-hours (25.28 × 106 MJ equivalent) of chilled water if MASH alarms were set up on every hood, indistinguishable to the annual energy usage of roughly 1149 households19. Further, the CO2 savings native those one thousand VAVs would be equivalent to removing about 435 vehicles from the road17. Together universities and also research institutions across the nation often have countless fume hoods ~ above site, the environment of MASH alarms can lead to far-reaching energy savings because that the nation as a whole. While the sash elevation sensors differ from hood come hood, if one to be to use the propagation the uncertainty approach based specifically on the anemometer used20 and a commercially accessible sash height sensor21, the result measurement uncertainty would be on the stimulate of ± 3%.

The gaue won incentives concerned the installation of these devices are likewise convincing. Each machine is fabricated utilizing an Arduino UNO, basic commercially-available peripherals, and corrugated plastic, which outcomes in a full cost of only $17.07 every device, and is more palatable than other potentially-risky strategies22. Because the device is inexpensive, the initial invest is miniscule contrasted to the yearly savings. In ~ a calculated price the $4.89 every cfm-year, in close commitment with the presented by Mills and also Sartor6 and 72% of the calculated through Wesolowski9, the projected savings per year, per hood, because of MASH alert installation is $1159 (assuming electricity prices of $0.11 per kWh the electricity, $0.082/ton-hour of cool water, and $8.346/klb the steam)14. Based upon material costs, a MASH alarm has actually a payback duration of 5.4 days. Further, the projected to save are likely to be conservative, offered that the trigeneration mechanism used at the MIT campus lowers the marginal price because that each unit that energy. Save will differ regionally depending upon variations in energy pricing (costs) and also weather (heat loads).

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MASH alarms could be enhanced by making them smaller and also even more cost effective. Smaller processors with comparable capabilities to the Arduino UNO to be explored, yet ultimately the Arduino UNO to be chosen because of convenience, and also cost-effectiveness. A future iteration the the MASH alarm can use a smaller, cheaper processor in enhancement to remove the built-in breadboard and directly soldering the contents together, i m sorry would increase the sturdiness the the machine and reduced the physical profile. The device could additionally use one ultrasonic street sensor and a Wi-Fi module to monitor the sash height of the hood and also log the data in addition to the alert feature. This could be provided to provide labs real-time feedback top top their as whole performance, which has actually been shown to minimize the energy wasted by fume hood use9. This additional feature would include an upfront material expense of just $15, as these usual Arduino parts are readily available for purchase.