## U.S. CONSUMER PRODUCT SAFETY COMMISSION

D IRECTORATE FOR 

## E NGINEERING 

## S CIENCES



### DEMONSTRATION OF A
REMOTE CARBON MONO XIDE SENSING
AUTOMATIC SHUT OFF DEVICE



## FOR PORTABLE GENERATORS

August 2006

Arthur Lee Electrical Engineer Division of Electrical Engineering Directorate for Engineering Sciences

This report was prepared by the CPSC sta ff and has not been reviewed or approved by, and may not necessarily reflect the views of, the Commission.August 2006 ii No Text on This PageAugust 2006 i Executive Summary

Gasoline-powered portable generators are wide ly used to provide back-up electrical power during extended power outages. One of the exhaust by-products from portable generators is carbon monoxide (CO), a colorless and odorless but highly lethal gas. In recent years, the proliferation and increased availabi lity of portable generators at th e consumer level have resulted
in an increase in the number of CO related deaths. This increase is particularly evident in areas that have lost electrical power for ex tended periods due to severe weather.

In an effort to mitigate the CO hazards associ ated with the use of portable generators, in 2005, the U.S. Consumer Product Safety Co mmission (CPSC) staff conducted a proof-ofconcept demonstration to integr ate a CO detection system with a portable generator. The concept utilizes wireless tec hnology combined with CO detec tion devices and off-the-shelf circuitry designed to provide an automatic shut o ff feature on portable gene rators. If elevated levels of CO accumulate in occupied areas of a household, the CO detection device sends a command to shut off the generator, thus eliminat ing the CO source. The following report details the design and testing of the demonstration system.August 2006 ii No Text on This PageAugust 2006 iii Table of Contents

Executive Summary .............................................................................................................. .........................i

1.0 Introduction............................................................................................................... ..............................1

1.1 CO Alarms.................................................................................................................. .........................1 1.2 Possible Technical Solution for Shutting Off a Portable Generator....................................................3

1.2.1 CO detection at the source............................................................................................... ............. 3
1.2.2 Remote CO detection ...................................................................................................... .............. 5

2.0 Wireless Communication with CO Al arms and Portable Generators.....................................................6

2.1 Test Setup and Instrumentation............................................................................................. ..............7 2.2 Incorporating a Wireless Transmitter in a CO Alarm .......................................................................10 2.3 Incorporating a Wireless Receiver on the Portable Generator ..........................................................12

3.0 Testing of the Remote CO Detection System .................................................................................. .....15

3.1 Test Button Testing ........................................................................................................ ...................16 3.2 Elevated CO Testing ........................................................................................................ .................17

4.0 Observations/Improvements .................................................................................................. ...............23

4.1 Power...................................................................................................................... ...........................23 4.2 Relays..................................................................................................................... ...........................24
4.3 CO Detection Unit.......................................................................................................... ...................24 4.4 Supervised System .......................................................................................................... ..................25 4.5 Wireless Range............................................................................................................. .....................25
4.6 Feed-Back Indicators....................................................................................................... ..................25
4.7 Self-Check................................................................................................................. ........................25

4.7.1 CO Detection Unit ........................................................................................................ .............. 26 4.7.2 Shut Off Unit............................................................................................................ ................... 26
4.8 Cost....................................................................................................................... .............................26

5.0 Summary.................................................................................................................... ...........................27

APPENDIX A Standard Operating Procedures for Assuring Minimum Carbon Monoxide Exposure During Demonstration of a Remote Carbon Monoxide Detection Shut Off Device for a Portable
Generator ...................................................................................................................... ............................... AAugust 2006 iv List of Figures

Figure 1. CO alarm helps detect elev ated levels of CO in the home ............................................................2

Figure 2. Portable generator located in confined spaces or near an open window .......................................3

Figure 3. Portable generator located in the garage of an attached home ......................................................4

Figure 4. Portable generator located outside in a semi-confined space ........................................................5

Figure 5. CO detection device to re motely shut off the generator ............................................................... .5

Figure 6. Block diagram of a shut off device on a portable generator..........................................................7

Figure 7a. Example of a CO detection unit in a small home ...................................................................... ..9

Figure 7b. Example of multiple CO de tection units in a larger home ........................................................10

Figure 8. RF transmitter installed in a CO alarm............................................................................... .........11

Figure 9. Schematic of CO alarm and RF transmitter............................................................................. ....11

Figure 10. Block diagram of receiver unit operation ............................................................................ ......13

Figure 11. Wireless receive r and shut off unit ................................................................................. ...........14

Figure 12. Schematic of shut off unit and generator............................................................................ .......14

Figure 13. Wireless receiver/shut off unit on the generator.................................................................... ....15

Figure 14. Adapter Response.................................................................................................... ..................16

Figure 15. Voltage response for remote shut off using the test button .......................................................17

Figure 16. Test 1 set-up with remote CO detection/shut off unit in the garage ..........................................18

Figure 17. Remote CO detection/shut off un it in the garage disabling the generator.................................19

Figure 18. Test 2 set-up with remote CO detection/shut off unit in the hallway ........................................20

Figure 19. Remote CO detection/shut off un it in the hallway disabling the generator...............................21

Figure 20. Test 3 set-up with remote CO detection/shut off unit in the kitchen.........................................22

Figure 21. Remote manual shut off of the generator from the kitchen .......................................................23

Figure 22. Powering the receiver unit.......................................................................................... ...............24August 2006 1 1.0 Introduction

Gasoline-powered portable generators are wide ly used to provide back-up electrical power during extended power outages. The popularity and availability of these devices began to increase during pre-Y2K (year 2000) as consumer s prepared for possible long-term power losses
associated with the Y2K conversions. Alt hough portable generator sales peaked in 1999 * , their relatively low cost and availability at the reta il level continued even after year 2000. Following
the Northeastern blackout of August 2003, many consumers considered generators to be a necessity in an emergency, similar to candles, fl ashlights, batteries, and bottled water. Major home improvement chains shipped thousands of addi tional generators to stor es in affected areas within days after power was restored. †

Most portable generators use a single cylin der, gasoline-fueled, internal combustion engine equivalent to a lawn mower engine. Although robust a nd rugged, these engines are inefficient and contain no emission controls to mitigate harmful exhaust, thus making them significant producers of carbon mon oxide (CO), a colorless and odor less but highly lethal gas.
Available data show that CO-related deaths occur when portable gene rators are improperly located in enclosed spaces or inadequately vented locations ‡ such as garages or near open windows and doors. Consumers locate generators indoors or close to hou ses for a number of reasons, including fear of theft and concerns th at direct exposure to precipitation may damage
the unit.

One concept to address the CO hazard is to incorporate a control system into the generator to shut it off or prev ent it from starting if CO levels constitute a significant risk to occupants in an area being monito red. The approach is to use a standard residential CO alarm
with a wireless link that will co mmunicate with a transmitter/receiver affixed to the portable generator. In the event that the CO alarm senses elevated concentrations of CO, the wireless link will communicate with, and automatical ly shut off, the generator.

Figures, illustrations, an d test setups shown or descriptio ns of tests conducted in this report show a generator that has purposely been improperly located in order to evaluate the effectiveness of the experimental system in sensing accumulated CO. The CPSC recommends that portable generators never be operated in a confined space, such as a garage. Portable generators should be operated and maintained as specifi ed by the manufacturer.

1.1 CO Alarms

Alarms to detect elevated levels of CO in the home have been available to consumers since the early 1980s. In 1992, Unde rwriters Laboratories (UL) pub lished the first edition of UL 2034, Standard for Safety for Single and Mult iple Station Carbon Monoxide Alarms . Initially,

* Donaldson, Mary, Portable Generators , CPSC Memorandum to Janet Buyer, Project Manager, U.S. Consumer Product Safety Commission, Washington, D.C., August 22, 2005.

† Generators: Power in a Pinch, Consumer Reports, Consumers Union of U.S., Inc, November 2003.
‡ Marcy, Natalie and Debra Ascone, Incidents, Deaths, and In-Depth Investigations Associated with Carbon Monoxide and Engine-Driven Tools, 1990-2004, CPSC Memorandum to Janet L. Buyer, Project Manager, U.S. Consumer Product Safety Commission, Washington, D.C., December 1, 2005.August 2006 2 CO alarms were plagued with re liability challenges, particularly false alarms. In response to these concerns, UL 2034 was modified to improve th e reliability of residential CO alarms.

CO alarms allow the detection of elevated levels of CO in a home from fuel burning appliances, as shown in Figure 1. The early detection of elevated levels of CO is critical to ensuring that affected occupant s have sufficient time to evacuate, before being overcome by dangerous levels of CO. Some jurisdictions in th e U.S. require the installation of CO alarms for homes containing fuel-burning ap pliances. Others, such as Mecklenburg County in North Carolina, require them in homes regardless of whether they contain fuel -burning appliances in response to CO deaths that occurred in a D ecember 2002 ice storm due to portable generators and burning charcoal. Most homes in the U.S. th at use fuel-burning appliances are not required
to have CO alarms installed.

CO alarm

Source of CO - Misaligned exhaust pipe

Figure 1. CO alarm helps detect elevated levels of CO in the home

The three basic types of CO sensors used in residential CO alarms are biomimetic, metal oxide, and electrochemical. Biomimetic (chemiopt ic) sensors are designed to mimic the way the body responds to carbon monoxide. These sensors use gel-coated discs that darken in the presence of CO, thus tripping the alarm. There ar e several advantages to biomimetic sensors. They are inexpensive and require very little electricity. The sensors typically do not nuisance alarm in the presence of comm on household gases. However, CO alarms equipped with these sensors may false alarm if there are high or low temperat ures and/or relative humidity levels in
the home.

The first residential CO alarms on the market used metal oxide or tin oxide sensors. These sensors use heated tin dioxide, which reac ts to carbon monoxide, to determine the level of CO. These units use more electricity than the bi omimetic or the electrochemical sensors because the tin oxide has to be heated every few minut es. Metal oxide sensor s respond quickly to CO, but may sometimes nuisance trip from exposur e to common household chemicals. HighAugust 2006 3 humidity can also be a problem, since the sensors degrade slightly each ti me they are exposed to
moisture. §

Electrochemical technology uses three platinum elec trodes in an electr olyte solution. The sensor generates energy when exposed to CO. These alarms respond quickly to CO, but their
sensors have a shorter life th an the other sensor types.

1.2 Possible Technical Solution for Shutting Off a Portable Generator

Deaths have occurred in scenar ios in which portable generators were placed inside or too close to a home, as shown in Figure 2. Since portable generators produ ce significant amounts of CO, the build-up of lethal concentrations of CO in a home can occur in a short amount of time.

Source of CO - Generator located in the garage

Source of CO - Generator located
in basement Source of CO - Generator located near open window

Figure 2. Portable generator located in confined spaces or near an open window

Before sending a shut off signal to the generato r, the level of CO in the affected area(s) must be monitored. There are at least two po ssible techniques to measure the CO produced by the generator. One method is to detect the level of CO in the vicinity of the generator (at the source). If levels near the ge nerator become elevated, an auto shut off device can disable the generator. Another method is to monitor the CO level in the vi cinity of the occupants in the home (remote detection). If elevat ed CO levels are detected in the home, an auto shut off device can disable the generator. There are adva ntages and disadvantages to each method.

1.2.1 CO detection at the source

Mounting a CO detection device on the generator allows fast de tection of elevated CO in a confined space as shown in Figure 3. Even though this method may be ideal for fast detection of CO, there are some design obstacles. Generato rs are typically used outside, which can cause
the CO sensors to become contaminated or di rty. The difficulty lies in designing a housing to shield the sensor from contaminants, but which w ill also allow air to enter the sensor chamber. In addition to withstanding the environmental cond itions, the electronics a nd sensor(s) must also

§ Phillips WG. Carbon monoxide detectors: What you need to know. Popular Science. 1998 Jan:76-81August 2006 4 withstand the conditions produced from the generator, such as c ontinuous vibration present with most generator engines.

CO sensor located on generator
detects elevated levels of CO CO cloud

CO cloud for illustration purposes. CO is colorless and odorless

Figure 3. Portable generator located in the garage of an attached home

The location of the sensor on the generator and the sensor’s sensitivity will be critical in preventing false alarms and still allowing the sensor to detect elevated levels of CO. Depending on objects adjacent to the generator, such as a wa ll, bushes, car, or shed, small pockets of CO may be trapped. An effective CO alarm shoul d be able to discriminate between a small temporary pocket of CO and a potentially lethal cloud. Small pockets of CO may cause the sensor to alarm and shut off the generator even though CO has not entered the home. Wind direction may also cause the CO sensor to shut off the generator, causing nuisance tripping of the
generator.

Even though CO levels are not elevated in th e home, CO levels may be elevated near the generator, which may present a risk to the consum er. The generator may be located outside in a semi-confined space, such as a carport, that ma y cause elevated levels of CO only near the generator. The consumer may be within the ha zardous CO cloud during re fueling or operation of the generator as shown in Figure 4.August 2006 5 CO cloud

CO cloud for illustration purposes. CO is colorless and odorless

Figure 4. Portable generator locat ed outside in a semi-confined space

1.2.2 Remote CO detection

Locating a CO sensor remotely allows monitoring the level of CO where the concentrations are most critical, as shown in Fi gure 5. One advantage of placing the CO sensor in the living space near the occupants is that it reduces the likelihood of the sensor being compromised by exposure to harsh environments. The alarm will also be more audible to the occupants, alerting them to elevated levels of CO. If the sensor unit contains a visual display of CO concentration, such as parts per million (ppm ), it will provide occupa nts with an indication of the level of CO to determine if it is rising or stable. If occupants observe rising CO levels, they could remotely shut off the generator with out having to approach it, thereby potentially reducing exposure to higher CO le vels that may be present cl oser to the generator. A disadvantage to remote sensing is that the CO se nsing unit might not be lo cated in the same part of the house in which occupants are located. In su ch a case, the level of CO near the occupants could be elevated, but the CO sensing unit may not de tect it because it is in a different part of the
home.

Generator shuts-off remotely Remote unit detects
elevated levels of CO

Figure 5. CO detection device to remotely shut off the generatorAugust 2006 6 Both types of CO detection/shut off concep ts, either at the sour ce or remotely, would require the CO sensing unit to operate with a battery or secondary pow er supply during a power outage. However, the “source” CO sensor located at the generator could switch to AC generator power once the genera tor has started.

2.0 Wireless Communication with CO Alarms and Portable Generators

CPSC staff evaluated the concept of using a remote CO detection device to detect elevated CO concentrations and remotely shut off the portable generator. In a December 2003 joint effort with the Naval Research Labor atory (NRL) under contract to CPSC (CPSC-I-02- 1290), the feasibity of incorpora ting wireless technology in batte ry-powered smoke alarms and having the alarms “communicate” with each other was demonstrated.

Under the 2003 contract with NRL, transmitte r and receiver circuits were successfully integrated into existing residen tial smoke alarms using wireless technology. If any smoke alarm activated, it transmitted a signal to the other smoke alarms so that they would activate “sympathetically.” Each receiving smoke alarm also acted like a repeater; thus, a smoke alarm that may have been too far away to be activated by the initiating smoke al arm could be activated by a closer smoke alarm that was transmitting an alarm signal. Maximizing battery power was a key factor in selecting the transmitting range and the rate at which the receiver checked for an alarm signal.

The demonstration described in this report us es wireless technology with a CO alarm to trigger a shut off device on the portable genera tor. The remote CO alarm was designed to initially check the CO level in the home before al lowing the occupant to star t the generator. This feature may also be beneficial in helping prevent the occupant fr om restarting the generator when
there are elevated levels of CO in the home.

A wireless transmitter that triggers a shut off device on the portable generator was incorporated into a conventional CO alarm. A shut off device was located on the generator where it will shut off the engine in the event of elevated CO leve ls in the home. Figure 6 shows a block diagram of a remote CO sensing shut off system. The user would be required to depress an enable button before the generator would be allowed to start. The enable button would prevent the operator(s) from star ting the generator when an elev ated level of CO may already
exist in the home.August 2006 7 Check for CO

User attempts to start generator

Power remote

CO unit

CO below
threshold CO above
threshold

Disable safety
interlock switch for xx minutes Safety interlock
switch enabled for xyz minutes

< xx minutes > xx minutes User presses
enable button

Timer >xyz minutes <xyz minutes

Figure 6. Block diagram of a shut off device on a portable generator

2.1 Test Setup and Instrumentation

CPSC staff conducted tests using a UL listed CO alarm, AC-powered with battery backup and electrochemical sensing, as the sensing device to signal the controls to shut off a generator. For this testing, the CO alarm wa s powered only from a battery (no AC power) to enhance the portability of the sy stem. The CO alarm also incorporated an interconnect feature that would allow multiple CO alarms to sound when any one of the units alarmed. This feature increases alarm audibility throughout the home. For the purposes of the staff testing, the interconnect signal was used to trigger the wire less transmitter that was installed in the CO
alarm.

A data acquisition system consisting of a cu rrent meter, an anal og-to-digital signal converter (ADC) unit, a gas analy zer, and a computer was used. The current meter was used to measure the load on the generato r during the tests. The ADC un it was used to record load current, CO alarm interconnect signal, CO level, and generator operating stat us (whether or not it was running). The CO alarm and gas analyzer (CO sampling device) were moved to different
locations in the home to record CO levels.

Below is a list of the equipment used in the staff testing. CPSC does not endorse the equipment and instrumentation used in the tests nor state that the equipment and instrumentationAugust 2006 8 used are the best or only products for this application. The product and company names listed
are trademark or trade names of their respective companies.

Alarm Source Residential Carbon Monoxide Alarm AC powered with 9- volt battery back-up Sensor Type - electrochemical
UL listed

CO Sampling NOVA Gas Analysis Equipment
Model 310WP Sensor Type – electrochemical Aspirated air sampling Range: 1% of full scale, 0-2000 ppm Response time: 20-30 seconds for 90% of step change Last calibrated – August 2002

Digitizing System Data Translation
Model DT9834
16 bit A/D

Computer Laptop 3GHz processor
1G RAM

Current Probe Fluke
Model 80i-110s Rated 10 milliamps to 100 Amps

Transmitter and Receiver Wireless Automator Programmable relays 6 relays rated at 3 amps @ 12V

High Current Relay Type - SPDT Fo rm "C" heavy duty dry contacts Contact rating 7A @ 30VDC, 10A @125VAC Input trigger 9-12VDC 30mA

Portable Generator 5250 watt
Fuel - Gasoline
Pull start

The transmitter and receiver units were part of an off-the-shelf remote-controlled relay unit that can control power for up to six 5-ampere appliances. The transmitter had three channels with a range of 150 ft. The rece iver unit included six relays th at were opened or closed by a signal from the transmitter. Depending on which push button(s) was depressed on the transmitter, the receiver unit could operate different relays.August 2006 9 The receiver unit was mounted on the generator to control a relay that was incorporated into the generator ON/OFF circuit as a shut o ff device. Since the receiver unit could receive multiple programmed signals from transmitters, multiple CO alarm transmitter units could be located throughout a home to increase the num ber of areas monitored for CO accumulation. Monitored areas might include individual bedrooms and each level of the home. The number of
CO transmitter units installed in a home would, in part, depend on the location of occupants in the home, and the size and configuration of the home. Figure 7a shows an example of a small home, which may require only one remote CO unit. A larger home may require multiple remote CO units as shown in Figure 7b. In this example, the master bedroom is separated from the other
three bedrooms. A remote CO detection unit would be needed in both areas if each area contained occupants. An additi onal remote CO unit might also be needed in the family room. For the purposes of this test program, only a single CO alarm transmitter unit was used.

Living Room Dining
Room Kitchen

Bedroom 2 Bedroom 3 Bedroom 1 DN Generator located outside back door

Figure 7a. Example of a CO detection unit in a small homeAugust 2006 10 Kitchen Family Room

Living Room Dining Room Master
Bedroom Breakfest
Room Screened Porch

Utility/ Laundry Room

Garage

Remote CO Detection Unit Vaulted Ceiling

UP

First Floor

Bedroom 2 Bedroom 3

Bedroom 4 Loft

Attic storage

Vaulted Ceiling Open to
below DN

Second Floor

Generator located outside screened porch

Figure 7b. Example of multiple CO detection units in a larger home

For staff testing, a 3,900 ft 2 home was used as the test structure. The home had an attached three car garage. The home had tw o levels and a basement. Each level was approximately 1,300 ft 2 . The home contained central heat ing and air conditioning, which were turned off during the testing. All the external windows and doors were closed during the testing.

2.2 Incorporating a Wireless Transmitter in a CO Alarm

To demonstrate this application using wirele ss technology, CPSC sta ff used off-the-shelf universal radio frequency (RF) transmitter and receiver units. The RF transmitter circuit board was removed from its plastic housing and installe d in a CO alarm, as shown in Figure 8. The transmitter circuit board was 1.25 inches x 1.5 inches, which allowed it to f it in the 9-volt battery compartment. A separate 9-volt battery termin al was used to power the CO alarm. The transmitter circuitry used one 12-volt battery.August 2006 11 Wireless transmitter mounted in the battery compartment

CO alarm with start-up safety interlock button Emergency Shut-Off
Press Test Button

Figure 8. RF transmitter installed in a CO alarm

The interconnect signal on the CO alarm was used to trigger the transmitter, which is normally activated by the pushbuttons on the transmitte r. Staff fabricated a circuit to interface
the transmitter with the CO alar m’s interconnect output signal. Figure 9 shows the schematic of how the wireless circuitry was incorporated into the CO alarm. The transmitter could send two
different commands to the receiv er. One command would initia te the allowable period for starting up the generator, and the other command wa s used to shut off the generator if the CO
alarm went off.

CO Alarm Wireless Circuit

Interconnect
Alarm Signal Channel 1 Channel 2 9 V battery Push button to enable generator

Figure 9. Schematic of CO alarm and RF transmitterAugust 2006 12 2.3 Incorporating a Wireless Receiver on the Portable Generator

The receiver/shut off unit was installed on a portable generator. The unit contained a wireless receiver, a separate sh ut off relay, and a rechargeable battery. Figure 9 shows a block diagram for the operation of the receiver un it and its integration with the generator.

The receiver unit is normally in a “stand-by” mode, waiting for a wi reless start-up signal from the CO detection unit. The generator st art-up sequence begins when the user presses a
button on the remote CO detection unit to transmit a start-up signal. When a signal is received, the receiver unit closes relays, which prepares th e generator for start-up and operation. The startup relay is closed for approximately 20 minutes, which gives the user time to go outside to the generator and continue the starting sequence, such as pull starting the engine. When the generator starts, the power to maintain closure of the relay (initially battery power) is replaced by the generator. If 20 minutes has elapsed and th e generator has not been started, the relay opens and disables the generator. The user would have to press the start-up bu tton on the CO detection unit again before attempting to start the generator.

Once the generator has been st arted, if elevated CO leve ls are detected by the CO detection unit, the CO detection unit transmits an RF signal to th e receiver unit. Upon receiving the signal, the receiver unit removes power fr om the relay, causing it to open and disable the generator. The generator will be disabled until the CO levels drop and the detection unit stops sounding/transmitting. Once the CO levels have declined, the start-up button can be pressed, and
the user will be able to start the generator within the 20 minute window.August 2006 13 Receiver determines

if start-up signal

or elevated CO signal Elevated CO signal Start-up signal

Timer
20 minutes

User attempts to start generator

High Current Relay Powered by generator High Current Relay Opens Timer expires

Generator Stops Generator Running Disconnect Power to Relay Power Relay Timer
1 minute

Generator Starts Programmable Relay Closes Programmable Relay Opens Reciever/Shut-off Unit awaiting signal

Figure 10. Block diagram of receiver unit operation

The receiver and shut off system were pack aged in an 8 x 3 x 2 inch box, which also contained the back-up battery, high current relay, and a sma ll circuit board. The wireless receiver with the programmable relays was moun ted on the outside of the box as shown in Figure
11. The wireless receiver had a 10-inch ante nna and required 12 volts input to power theAugust 2006 14 circuitry. An AC/DC connector was used to allow charging of the back-up battery by either plugging the adapter into a household 120 VAC r eceptacle or into the generator’s 120 VAC receptacle. Another connector was used to conne ct the shut off relay to the generator’s manual ON/OFF switch. For prototype designing and tes ting, this set-up allowed easy removal of the receiver/shut off unit. Figure 12 shows the schematic of the wireless circuitry incorporated in the
test generator.

Receiver Unit and Shut-off Circuitry

Battery Back-up and High Current Relay Wireless Circuitry and Programmable Relays Wireless Receiver and Programmable Relays

Battery Back-up and High Current Relay Receiver Antenna

AC/DC Adapter/Charger

Connector to Generator Switch

Programmable Relays

High Current Relay

Battery Back-up

Figure 11. Wireless receiver and shut off unit

Figure 12. Schematic of shut off unit and generatorAugust 2006 15 The wireless receiver/shut off unit was m ounted on the generator and connected to the generator’s manual ON/OFF switc h as shown in Figure 13. Th e generator’s ON/OFF switch
remained in service and allowed the user to shut off the generator by turn ing the switch to the OFF position. The generator also could not be st arted unless the switch was in the ON position. The receiver unit’s relay was connected in parallel with the manual ON/OFF switch. (The ON/OFF switch is open in the ON position and clos ed in the OFF position, so either switch can be used to shut off the generator.) This arrange ment allowed either the user to manually shut off the generator or the receiver uni t to shut off the generator.

Manual Shut-Off Switch

Receiver Antenna

Connector for battery back-up AC/DC Adapter/Charger

Connector to Generator Switch

Wireless Receiver
and Shut-Off Unit Manual Shut-Off Switch AC/DC Charger

Wireless Receiver and Shut-Off Unit Mounted on Generator

Figure 13. Wireless receiver/shut off unit on the generator

The shut-off relay current capacity was dete rmined by measuring the current through the
ON/OFF switch when the switch was turned from ON to OFF with the ge nerator running. The peak current was less than 2 amps, and the pulse width was less than 0.5 seconds. The current through the generator’s manual ON/OFF switch was less than the maximum current rating for the high current relay select ed for the shut off unit.

3.0 Testing of the Remote CO Detection System

Several tests were conducted to determine the functionality of the CO detection and shut off system. The testing was conducted using the test button on the CO detection unit and the receiver unit mounted on the gene rator. Several tests were conduc ted to allow the CO detection unit to be exposed to elevated levels of CO a nd then shut off the generator automatically. The elevated levels of CO were generated by opera ting the portable generato r in a confined space (6993 ft 3 garage). As previously noted, testing conducted with the porta ble generator in the garage was for test purposes only and is not c onsistent with correct and safe operation of a portable generator. The CPSC recommends agains t operating a portable generator in a garage. Portable generators should be operated and maintained as specified by the manufacturer.August 2006 16 For all the tests, an AC/DC (120 VAC/ 5VDC) transformer was plugged into the generator’s 120 VAC receptacle and used as a mon itoring source to indicate that the generator was running. Figure 14 shows the response of th e AC/DC adapter when power is removed. The voltage slowly decays after a dela y of approximately 3 seconds. The delay and decay are caused by internal adapter capacitance.

A DC Adapter voltage curve

0 1 2 3 4 5 6

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47
Time (seconds)Voltage Powering the adapter

Power removed adapter response

approximately 3 s delay before decay

Figure 14. Adapter Response

The NOVA Gas Analyzer used in the testing was last calibrated in 2002 so the measured values were only used for monitoring purposes in the course of these tests. The purpose of using the CO gas analyzer was to roughly monitor the CO build-up during the test. The reading was
also used to determine when the CO level in th e home had reached near zero before starting the
next test. The unit was zeroed before each test. A data acquisition system was used to record CO levels, the CO detection uni t’s interconnect signal, and the output of the AC/DC transformer plugged into the generator. The sampling rate was 0.1 seconds unless noted otherwise.

3.1 Test Button Testing

Initial testing was conducted using the test button on the CO alarm. This test was
conducted outdoors. The CO detection unit was placed approximately 20 feet from the generator. The test button on the CO unit was depressed, which enabled the generator to be started. The generator was started successfully and, after 20 minutes, the relay timed out but remained closed utilizing power from the generator. No external load was connected to the
generator.

After 30 minutes, the test bu tton on the CO detection unit wa s depressed. The receiver unit received the signal and opened the relay, causing the generator to stall and shut off. FigureAugust 2006 17 15 shows the voltage response curves for the interconnect signal a nd the generator power shutting off. The sharp peaks show the intercon nect signal triggering the wireless transmitter. Approximately 0.5 seconds later, the power at the generator’s 120 V receptacle was discontinued. The adapter response delay and decay are also shown in the figure.

Interconnect Signal and Generator Shut-Down

-1 0 1 2 3 4 5 6 7 8 9

Time (0.25 second per tick)Voltage

Generator power Alarm interconnect Generator engine stops Wireless interconnect signal transmitted

Indicator of generator running

Indicator of wireless interconnect signal Generator begins
shut-down

adapter response Generator engine stops Generator begins
shut-down

Figure 15. Voltage response for remote shut off using the test button

3.2 Elevated CO Testing

The generator was located in a three car gara ge attached to a two- story (with basement) single family home. The CO detection unit was pl aced in various locations in the home for each test. The home has an open floor plan and 9 ft ceilings. The family room has cathedral ceilings to the second floor, and the foyer is two storie s high. Together, the first floor, second floor, and basement are approximately 3,900 ft 2 . The three car garage is approximately 31.5 feet x 18.5 feet x 12 feet high. The generato r was placed in the middle bay of the three car garage, and all the garage doors were closed for all the test s. The generator was placed with the exhaust directed towards the middle garage door. The garage did not contain any vehicles, but the miscellaneous items in the garage occupied approximately 1/12 of the garage’s volume. The garage has a door leading to a hallway. The ad joining hallway includes an open staircase down to the basement, an interior door to the general living area and an exterior door to the outside.

The home’s heating and air conditioning syst em was off for all the tests. All the
windows and external doors were closed for a ll the tests. During the testing, the ambient temperature varied from 70° F to 76° F, and the winds were variable from 5 to 10 mph.August 2006 18 For the first test, the CO de tection unit was placed in the garage near the door to the hallway. The remote detection/shut off unit wa s approximately 14 feet from the generator and 3-
1/2 feet from the floor. The door to the hall way was closed. The te st was conducted with no load. The gas analyzer was placed at the same location as the CO detection unit. Figure 16 shows the setup for the testing.

Open

Closed Closed

Garage door
closed Garage door
closed Garage door
closed CO CO Detection Unit

Gas Analyzer

Data Acquisition System Generator with Shut-off Unit To living area

T o

b a s e m
e n

t

No Load Test a p p

r o x i m

a t e l y 1

4

f t

both units approximately 3.5 ft from the floor

Figure 16. Test 1 set-up with remote CO detection/shut off unit in the garage

The start button on the CO detection unit wa s depressed, which enabled starting of the generator. The generator was pull-started succe ssfully and the operator monitored the testing
from an outdoor location. After the start of the generator, th e CO detection unit detected elevated CO levels in approximately 8 minutes. At this time, the CO detection unit transmitted a wireless signal. The receiver unit received the signal and shut off the generator. The gas analyzer indicated approximately 732 ppm, and th e CO detection unit’s di gital display indicated 598 ppm when the generator shut off. Figure 17 shows the interconnect signal from the CO detection unit, the generator runn ing power indicator, and the CO gas analyzer over a 15 second period.

The garage and exterior doors were opened and CO levels we re allowed to drop to near zero before the operator re-entered the structure. The gas analy zer was zeroed before the next

test.August 2006 19 Test 1 Generator Shut-Down - Remote in Garage

0 2 4 6 8 10 12

495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510

Time (seconds)Voltage

700 710 720 730 740 750 760 770CO Level (ppm)

Alarm Interconnect Signal Generator Power CO Level Generator engine stops G a s A n a l y z e r

Figure 17. Remote CO detection/shut off unit in the garage disabling the generator

In the second test, the CO detection unit and CO gas analyzer were moved to the hallway, adjacent to the garage. As shown in Figure 18, the CO detection unit and the CO gas analyzer were approximately 4 feet from the door leading from the garage to the hallway. The door was ajar approximately 3/8 inch to allow an extensio n cord from the generato r to be connected to a refrigerator in the kitchen. The door from the hallway to the living area was closed with the extension cord to the refrigerato r routed under the door air gap, which was approximately 1 inch high. The load on the generator varied from n ear 0 amps to 2 amps, depending on whether the refrigerator’s compressor was operating (which amounted to approximately 4.5% of its rated load capacity). The sampling rate of the data acquisition system was set at 1 second.August 2006 20 Closed Partially
closed

Garage door
closed Garage door
closed CO CO Detection Unit

Gas Analyzer

Data Acquisition System Generator with Shut-off Unit

Extension cord to refrigerator To living area

T o

b a s e m
e n

t Closed

both units approximately 3.5 ft from the floor

Garage door
closed Distance 4 feet from the door

Figure 18. Test 2 set-up with remote CO detection/shut off unit in the hallway

The start button on the CO detection unit wa s depressed, which enabled starting of the generator. The generator was pull-started successf ully. After about 17 minutes, the gas analyzer measured approximately 532 ppm in the hallway. At this time, the CO detection unit began to alarm, which caused the unit to transmit a signal to the receiver unit. The receiver unit received the signal and the genera tor stalled and shut off, as shown in Figure 19. In examining Figure 19, the graph makes it appear as though the generator began to shut off before the CO detection unit triggered the transmitter. This was because the digitizing system sampling rate of 1 second was not frequent enough to capture th e first pulse signal from the CO detection unit. The CO detection unit’s LED indicated 520 ppm when the generator was shut off.

The garage and exterior doors were opened and CO levels we re allowed to drop to near zero before the operator re-entered the structure. The gas analy zer was zeroed before the next

test.August 2006 21 Test 2 - CO Detection Unit in Hallway (generator located in garage)

-1 0 1 2 3 4 5 6 7 8 9

0 100 200 300 400 500 600 700 800 900 1000 1100

Time (seconds)Voltage

-100 0 100 200 300 400 500 600CO Level (ppm)

Generator power Alarm interconnect CO (Nova) G a s A n a l y z e r

Figure 19. Remote CO detection/shut off unit in the hallway disabling the generator

In the third test, the CO dete ction unit and CO gas analyzer were moved to the kitchen, adjacent to the hallway to the garage. The door leading from the garage to the hallway was opened 3/8 inch to allow the extension cord from the generator to be connected to the refrigerator. The door leading from the hallway to the kitchen was opened fully. Figure 20 shows the setup for the testing.August 2006 22 Closed Partially
closed

Garage door
closed Garage door
closed CO

Generator with Shut-off Unit

Extension cord to refrigerator To living area

T o

b a s e m
e n

t T o b a s e m e n t

open both units approximately 3.5 ft from the floor

Garage door
closed To foyer To dining

room

Kitchen

Open to family room Refigerator

CO Detection Unit

Gas Analyzer Data Acquisition System

Distance 5 feet from the exterior door closed

T o

s e c o n d

f

l o o

r

Figure 20. Test 3 set-up with remote CO detection/shut off unit in the kitchen

The start button on the CO detection unit wa s pressed, which enabled starting of the generator. The generator was pull-started su ccessfully. After almost 1 hour of generator operation, the CO gas analyzer measured 90 ppm in the kitchen. Note that the CO levels in the
kitchen did not reach the threshold level for the alar m to activate. To test the remote manual shut off of the generator, the test button was pressed on the CO detection unit, causing it to transmit a shut off signal. The receiver unit received the signal, causing the generator to shut off as shown in Figure 21. The LED display on the CO alarm displayed 82 ppm when the generator had shut off. The remote manual shut off of the generato r allowed the tester to stop the generator without entering the garage which, based on earlier testing, most likely contai ned elevated levels of CO. In the first test, the CO levels in the garage m easured over 700 ppm in 8 minutes. For this test, the generator was operating for almost 60 minutes be fore being shut off. The actual CO level in the garage was not measured.

As demonstrated in test 3, the remote shut o ff device could be very be neficial in that it could allow the user to shut the generator off remotely (without having the user enter the area near the generator, which may contain high levels of CO).August 2006 23 Test 3 - CO Detection Unit in Kitchen

-1 0 1 2 3 4 5 6 7 8 9

1500 1700 1900 2100 2300 2500 2700 2900 3100 3300

Time (seconds)Voltage

-40 -20 0 20 40 60 80 100 120CO Level (ppm)

Generator power Alarm interconnect CO (Nova) Manual remote shut-down signal. Generator shuts down shortly after.

G a s A n a l y z e r

Figure 21. Remote manual shut off of the generator from the kitchen

4.0 Observations/Improvements

The demonstration of the experimental CO dete ction/shut off system showed that it is possible to incorporate an auto s hut off system on a generator. The design of the experimental unit was based primarily on functionality and, ther efore, was not optimized for considerations such as cost, complexity, size, usability, and re liability. After building and testing the system,
staff concluded that there are features a nd technological improvements that could be incorporated in the CO detection and shut off sy stem that would increase the reliability, reduce the number of components, and simplify the system.

4.1 Power

The demonstration system tested used a rechar geable battery to power the receiver unit before it received AC power from the generato r. The system allowed the user to plug the AC/DC charger adapter into a regular household r eceptacle to charge the battery until needed. When needed, the user would unplug the AC/DC ch arger from the household receptacle and plug it into the generator’s 120 VAC receptacle as shown in Figure 22. This setup allowed the battery to be fully charged at all times so that the wire less circuit would always be energized, regardless
of the ON/OFF status of the CO detection unit.

A much simpler method, which could significan tly reduce both the si ze and cost of the receiver unit on the generator, would be to use a 9-volt battery to power a receiver unit equippedAugust 2006 24 with an ON/OFF power switch. The 9-volt battery w ould be used to power the receiver unit until the generator started. The usage life of the batte ry would be similar to its shelf life because of the short duration of the usage pe riod just prior to generator start-up. Typically, an alkaline battery can have a 5-year shelf life, which ma y vary with extremes in temperature.

Household receptacle

Stand-By Mode User wants to start generator (example - loss of household power)

User starts generator A C/DC Charger

Generator Start-Up Mode Receiver is powered by battery back-up AC/DC Charger

Generator Running Mode Generator with Shut-off Unit

Back-up battery being charged Receiver is powered by generator and recharges battery back-up A C/DC Charger

Figure 22. Powering the receiver unit

4.2 Relays

The demonstration system had six standard relays available and an additional high current relay. The six relays were programmed and controlled by the wire less circuitry. Each relay could be programmed separately. The re lays could be programmed to be momentary, latched, validity ** , 30-second timed, 1-minute timed, 5-minute timed, 20-minute timed, or strobed (repeated ON/OFF). Each relay could be used normally open (N.O.) or normally closed (N.C.) and was rated for 3 amps at 12 VDC. The s hut off system used only two of the six relays on the circuit board. The two relays were used to control the high curren t relay, which was rated at 7 amps at 30 VDC or 10 amps at 125 VAC.

The number of relays needed can be reduce d, and it is possible the high current relay could be eliminated. The six relay circuit board could also be reduced to one or two relays depending on the programming capabilities of the re lay circuit. Reducing the number of relays would also drastically reduce the size and cost of the receiver unit.

4.3 CO Detection Unit

A residential CO alarm was integrated with a wireless transmitter. The CO alarm used AC power with battery back-up. In the testing, only the battery back-up power source was used. Since the alarm was originally designed for hous ehold plug-in as the primary power, the alarm had an LED display, which required a significant amount of power. Most battery-only powered CO alarms use an LCD display to help minimize current usage.

** Only ON when pressed and OFF when released.August 2006 25 4.4 Supervised System

The demonstration system utilized an unsupervised wireless system. The shut off unit on the generator and the remote CO detection unit did not incorporate an additional check for communication integrity. The disadvantage of su ch a system is that it would allow a user to
disable the CO detection unit afte r starting a generator, thus leav ing occupants unprotected in the event of a CO build-up.

A supervised system would allow each of th e units, CO detection and shut off units, to
monitor each other. The CO detection and shut off units would each have a transmitter and receiver, or a transceiver. If the shut off un it on the generator did not receive a periodic check signal from the CO detection unit, the shut off unit would disable the ge nerator. If the CO detection unit did not receive a pe riodic check signal from the shut off unit, the CO detection unit would sound an alarm, indicating that it was out of range or the shut off unit had malfunctioned.

4.5 Wireless Range

The maximum range tested for the demonstrat ion unit was approximately 50 feet through one wall or door. The minimum required reliable wireless range between the CO detection unit and generator would need to be determined to ensure that the CO detection unit and generator
work as intended for consumers.

4.6 Feed-Back Indicators

The demonstration unit did not contain any f eed-back indicators to indicate that the system was operating correctly. Indicator lights on the shut off unit would allow the user to know the system status.

4.7 Self-Check

The demonstration unit did not conduct a self-check of the circuitry. Similar to a supervised system for wireless communicati on, the self-check woul d determine that the remainder of the circuitry in the CO de tection and shut off units was functioning.August 2006 26 4.7.1 CO Detection Unit

Self-check the CO sensor sensitivity

A periodic check of the CO sensor sensitivit y to determine if the sensor has become
more or less sensitive than manufacturer specifications would help prevent the CO alarm from nuisance alarming or not alarmi ng when elevated levels are present.

Low battery check

A low battery check in the CO alarm unit w ould allow the user to change the battery before the system becomes nonfunctional.

Transceiver circuitry is functioning

A self-check of the transceiver circuitry w ould determine if the circuitry is functioning correctly.

4.7.2 Shut Off Unit

Self-check the relay circuitry

A self-check of the relay circuitry would determine if the circuitry is functioning correctly.

Low battery check

A low battery check in the receiver unit w ould allow the user to change the battery before the system becomes nonfunctional.

Transceiver circuitry is functioning

A self-check of the transceiver circuitry w ould determine if the circuitry is functioning correctly.

Continuity with the manual ON/OFF switch

A continuity check of the manual ON/OFF switch would determine if the receiver unit is connected to the generator and has not been disabled or bypassed.

4.8 Cost

Off-the-shelf components used in the demons tration included an AC-powered CO alarm with battery back-up, which retails for approximate ly $52. The CO alarm cost would be lower if it was only battery powered and contained an LCD instead of an LED display. The off-the-shelfAugust 2006 27 wireless transmitter and receiver system cost a pproximately $100 (retail). The system contained more features than were actually required in the demonstration unit and more features than would be required in a production unit. For ex ample, the unit was programmable, which was a useful feature for prototyping but unnecessary for production units. Additionally, although the demonstration unit contained six relays, only two were used in the system. This number could probably be further reduced to one relay with careful circuitry design and programming. The high current relay used in thes e tests cost approximately $12 (re tail), which could have been omitted in the design. For the circuitry and the other associated hardware discussed above, the engineering staff estimates that a production unit could add an additional $100 to the cost of a portable generator. The average cost of a retail CO alarm is approximately $30 and the wireless circuitry would be an additional $50 to $70. Th e additional cost would depend on many factors, such as the manufacturer’s approach and prev ious experience in using wireless technology, technique for interfacing the shut-off circuitry wi th the generator, and type of CO alarm. In addition, there could be additional costs in producing a fi nal product that makes the system reliable, consumer friendly, and other factors that were not ex amined in this demonstration.

5.0 Summary

In recent years, the proliferation and increase d availability of porta ble generators at the
consumer level have resulted in an increase in the number of carbon monoxide (CO) related deaths. To help mitigate the CO hazards associ ated with the use of portable generators, the CPSC staff successfully demonstrated a concept to incorporate an auto shut off device on a portable gasoline-fueled engine gene rator that activates when elevated CO levels are detected in the home. A method of monitoring CO levels at a single location away from the generator was explored. If elevated CO levels are detected in the home, an au to shut off device can disable the
generator.

A demonstration system was designed and built to evaluate the con cept of shutting off a generator from a remote location when elevat ed levels of CO are detected. For the demonstration system, a wireless transmitter was incorporated into a CO alarm that was used as the initiating device to signal a sh ut off of the generator. A wi reless receiver and relays were used to shut off the generator.

Several tests were conducted to determine the functionality of the CO detection and shut off system. Testing was conducted using the te st button on the CO de tection unit with the receiver unit mounted on the gene rator. Several tests were conduc ted to allow the CO detection
unit to detect elevated levels of CO and shut o ff the generator remotely. In all the tests, the generator shut off when the CO detection unit transmitted a shut off signal. The CPSC staff viewed this program as a successf ul demonstration of the CO det ection/automatic generator shut off concept.

The study was limited to proof-of-concept and did not consider issues such as life expectancy, reliability, usability, and environmenta l conditions. All of these factors would need to be considered in developing a remote CO detection/shut-off sy stem for portable generators for

consumer use.August 2006 28 No Text on This PageDecember 2005 DRAFT A APPENDIX A

Standard Operating Procedures for Assuring Minimum Carbon Monoxide Exposure During Demonstration of
a Remote Carbon Monoxide De tection Shut Off Device
for a Portable GeneratorDRAFT December 2005 No Text on This PageDecember 2005 DRAFT A-1 

## Standard Operating Procedures

for Assuring Minimum Carbon Monoxide Ex posure During Demonstration of a Remote

Carbon Monoxide Detection Shut O ff Device for a Portable Generator

Prepared by Arthur S. Lee

Electrical Engineer

Division of Electrical Engineering

U.S. Consumer Product Safety Commission

August 2005

Version 2Page 2 of 7

Version 1 Date : August 2005 Standard Operating Procedures For Assuring Minimum Ca rbon Monoxide Exposure

Title: Guidelines and Procedures for Demonstration of a Remote Carbon
Monoxide Detection Shut Off Device for a Portable Generator

DRAFT December 2005 A-2 1.0 PURPOSE :

The purpose of this document is to specify appropriate procedures and safeguards for test personnel to follow to protect them from expos ure to potentially-harmful concentrations of carbon monoxide during testin g of a prototype remote CO detection/ automatic shut off system installed on a porta ble generator running indoors in an actual
residence. The nature of the testing is to intentionally repr oduce an inappropriate (albeit foreseeable) application of a portable gasolin e-fueled electric generator (operating it indoors) to evaluate the effectiv eness of the prototype system.

2.0 DEFINITIONS :

For purposes of this document, the following definitions apply:

Standard Operating Procedures

The recognized, acceptable cr iteria which serve as support for methods or manners of fulfilling a function or functions.

CO

Carbon Monoxide. The CO in this testing will be one of the components of the exhaust gasses produced by th e portable generator.

Portable Generator

The gasoline-powered engine-driven, electric generator that was outfitted with a radio-frequency (RF) receiver contro lling an engine shut off device.

Remote Carbon Monoxide Detection/Shut Off Unit

The carbon monoxide detection unit that was outfitted with an RF transmitter to send a signal to the receiver unit on the generator.

PPM

Parts per million. Units representing the concentration of carbon monoxide.

Manual Remote Shut Off Device

A hand-held transmitter that can be used to shut off the generator from a location
where accumulated CO is below hazardous levels.Page 3 of 7

Version 1 Date : August 2005 Standard Operating Procedures For Assuring Minimum Ca rbon Monoxide Exposure

Title: Guidelines and Procedures for Demonstration of a Remote Carbon
Monoxide Detection Shut Off Device for a Portable Generator

December 2005 DRAFT A-3 Gas Analyzer

A portable unit that measures the leve l of carbon monoxide w ith an accuracy better than 1% of the instrument’s full scale based on a 0-2000 ppm range and a response time of at most 30 seconds for a 90% step change; the unit must also be capable of remote monitoring.

3.0 SCOPE:

The testing is to demonstrate the prot otype CO detection/shut off unit as incorporated with a generator by detecting CO and remotely shutting off the generator in
an actual residence. The elevated levels of CO are to be generated by the portable generator in a confined space, such as a ga rage. The set-up and configuration of the testing to be conducted are for test purposes only and are inconsiste nt with correct and safe operation of a portable generator.

4.0 GUIDELINES:

Monitored CO levels

The level of CO in the test structure shall be monitored from the exterior of the test structure by two methods (r esidential CO alarm and a CO ga s analyzer). The level of
CO in the test structure shall be monitored in two areas of the test structure by residential
CO alarms.

Operator(s)

The operator(s) shall be at a minimum of 20 feet from the test structure during testing. The data acquisition system shall be located a minimum of 20 feet from the
exterior of the test structure. The inst rumentation and operator(s ) shall be upwind or adjacent to the test structur e during testing. DO NOT TEST if the instrumentation and operator(s) are downwind of the test structure.

Reentry

The operator(s) shall reenter the test st ructure only when the CO concentration readings from both monitors are below 5 pp m. The operator(s) may enter CO monitor
areas for less than 15 seconds if the CO le vels are below 95 ppm. This 15-second period for concentrations below 95 ppm is with in the OSHA PEL, NIOSH REL, and AGGIH TLV exposure limits for CO, as defined below.Page 4 of 7

Version 1 Date : August 2005 Standard Operating Procedures For Assuring Minimum Ca rbon Monoxide Exposure

Title: Guidelines and Procedures for Demonstration of a Remote Carbon
Monoxide Detection Shut Off Device for a Portable Generator

DRAFT December 2005 A-4 OSHA PEL

The current Occupational Safety and Hea lth Administration (OSHA) permissible exposure limit (PEL) for carbon monoxide is 50 parts per million (ppm) parts of air (55 milligrams per cubic meter (mg/m(3))) as an 8-hour time-weighted average (TWA) concentration [29 CFR Table Z-1].

NIOSH REL

The National Institute for Occupational Safe ty and Health (NIOSH ) has established a recommended exposure limit (REL) for carbon monoxide of 35 ppm (40 mg/m(3)) as an 8-hour TWA and 200 ppm (229 mg/m(3 )) as a ceiling [NIOSH 1992].

ACGIH TLV

The American Conference of Governmental In dustrial Hygienists (ACGIH) has assigned carbon monoxide a threshold limit value (TLV ) of 25 ppm (29 mg/m(3)) as a TWA for a normal 8-hour workday and a 40-hour workweek [ACGIH 1994, p. 15].

Remote Shut Off

The generator shall be capable of bei ng remotely shut off by two methods. One method must be a hand-held transmitter worn by the operator(s).

Effects of Carbon Monoxide

The operator(s) shall be familiar with the symptoms and effects of CO on a person. Signs and symptoms of acute exposure to carbon monoxide may include headache, flushing, nausea, vertigo, weakness, irritability, unconsciousness, and in persons with pre-existing hear t disease and atherosclerosis, chest pain and leg pain. (U.S. Department of Labor, Occupational Safety & Health Administration)

Generator

The gas tank will be filled with a maximum of 1⁄2 gallon of gas, limiting the run time to approximately 1 hour (7 gallons for 14 hours of operation)

Test Structure

All doors to the test structure not visibl e by the operator(s) sh all be locked to prevent persons from entering the test structure. The ope rator(s) shall carry keys to unlock any of the doors on the test structure.Page 5 of 7

Version 1 Date : August 2005 Standard Operating Procedures For Assuring Minimum Ca rbon Monoxide Exposure

Title: Guidelines and Procedures for Demonstration of a Remote Carbon
Monoxide Detection Shut Off Device for a Portable Generator

December 2005 DRAFT A-5 5.0 PROCEDURES:

5.1 Initial Verification of Hardware Operation

The operator(s) shall verify that the te st instrumentation and prototype test units are operational. The gas analyzer sh all not have a certification older than 5 years. The wireless transmission of the shut off signal from the CO detection unit to the generator shall be tested by using the test button on the CO detection unit. The manual handheld transmitter for generator shut off shall be tested prior to any testing.

5.2 Location of the CO source (generator)

The portable generator shall be located in a test structure that allows easy ventilation of the test room, such as a ga rage. The test room or garage shall be equipped with remote ventilation, such as wireless garage door openers and fan(s).

5.3 Location of the CO detection units

The CO detection unit shall be located in areas of the test structure that provide accurate monitoring of CO levels in areas where operator(s) ingress and egress would result in potential exposures.

5.4 Pre-Testing Safety Checklist

a. Gas analyzer reading of CO level in the structure is below 5 ppm
b. CO detection unit reading is zero

c. Generator gasoline tank filled with maximum of 1⁄2 gallon of gasoline
d. Instrumentation and data acquisition ready

e. Verify no person in the test structure
f. Zero gas analyzer before each test

5.5 Post Testing Safety Checklist

a. Generator has shut off
b. Stop data acquisition

c. Ventilate the test structure remotely
d. Monitor CO levels in the test structurePage 6 of 7

Version 1 Date : August 2005 Standard Operating Procedures For Assuring Minimum Ca rbon Monoxide Exposure

Title: Guidelines and Procedures for Demonstration of a Remote Carbon
Monoxide Detection Shut Off Device for a Portable Generator

DRAFT December 2005 A-6 6.0 INSTRUMENTATION AND EQUIPMENT SET-UP:

The following is a list of instrumenta tions to be used in the testing:

a. Residential Carbon Monoxide Al arm (AC powered with 9-volt battery back-up)
b. NOVA Gas Analysis Equipment (Model 310WP)

c. Data Translation (Model DT9834)
d. Dell Laptop Computer (Model 5150)

e. Fluke Current Probe (Model 80i-110s)
f. Street Smart Technologies Wireless Automator (Model WA6R)

g. Portable Generator (5250 watt)

The following diagram is an illustration of the test set-up for testing the CO detection/shut off system and the portable generator.

Closed

Ventilation Ventilation Ventilation CO CO CO

Data Acquisition System Remote Ventilation System Generator with Shut-off Unit

CO Gas Analyzer

Display of CO
Levels 20 feet minimum CO Detection Unit Residential CO
Alarms

Viewing window of
instrumentation Test StructurePage 7 of 7

Version 1 Date : August 2005 Standard Operating Procedures For Assuring Minimum Ca rbon Monoxide Exposure

Title: Guidelines and Procedures for Demonstration of a Remote Carbon
Monoxide Detection Shut Off Device for a Portable Generator

December 2005 DRAFT A-7 7.0 EMERGENCY PROTOCOL:

Intervention for CO Poisoning

1. At first signs of CO poisoning symptoms, shut off the generator
2. Go or move victim to a well-ventilated area
3. Dial 911