GB2356933A - Gas monitor with movement detector and data logging - Google Patents

Abstract

A gas monitor 1 includes CO, NO<SB>2</SB> and O<SB>2</SB> gas sensors 3, 4 and 5 and a movement-detecting device 8 for detecting movement of a person within a predetermined area. Data representing concentration of sensed gases and absence/presence of movement is recorded by a data logger 15 in correlation on a time basis as representing data obtained over the same time periods at predetermined intervals. Data downloaded from the logger may be presented in table form and will indicate the gas concentration values and the absence/presence of movement and the common times these indications were obtained. Such a monitor enables a room to be monitored for high levels of gases and absence/presence of an occupant at times of such high levels.

Description

2356933 GAS MONITOR The present invention relates to gas monitors and,

more particularly, to gas monitors. for detecting levels of concentration of one or more gases in the air.

Clean air is an important determinant of human health and comfort and for many years air pollution was considered to be a problem mainly with the outdoor environment. However i t is now recognised that people may spend more than 90% of their lives indoors and a large proportion of this time may be spent in their own homes. Indoor air is affected by factors such as cigarette smoke and allergens such as home dust mite. The burning of fossil fuels within a home may also affect indoor air quality.

Personal exposure to a variety of airborne contaminants in the home is acknowledged to present a potential risk to an occupant's health. This risk is determined both by the amount of pollutant present and the time for which an individual is exposed.

Over the past twenty years there have been numerous epidemiological studies linking the home environment with respiratory diseases. In some of these studies the data has been recorded by means of so-called personal badges where the occupant is asked to wear the badge. A common such badge comprises a passive gas sensor and the data (concentration of 2 gas in the air) is formed of average values logged for a short period of time, e.g. seconds /minutes. This is then normally complemented by diary sheets that the occupant is asked to keep and complete on a frequent basis. In these cases the reliability of the results is based on the accuracy of the diaries and the co-operation of the occupant wearing the badges.

Another way of obtaining such measurements indoors has been to use full size, pumped analysers which make use of infra red absorption technology. Heteroatomic gases absorb and radiate light energy in the infra-red region at a specific wavelength according to the chemical composition of the gas.

Such analysers measure the concentration of the gas according to the degree or extent of absorption. The analysers would be situated within a room with wires and tubes connecting the sample points to the inlet point of the analysers. The analyser produces an output signal which is normally logged onto either an internal logger or a separate data logger.

This arrangement has proven to be cumbersome, noisy and intrusive.

An object of the present invention is to provide a monitor which overcomes the disadvantages of the devices described above for indoor air quality monitoring.

3 According to the invention a gas monitor includes at least one gas sensor for detecting the concentration of a gas, a device for detecting movement of a person within a predetermined area, and a data recording means, the gas sensor and movement detecting device having respective data output means which communicate or connect with the data recording means whereby data representing detected concentration of gas and data representing presence or absence of movement, respectively, is input into and recorded by the data recording means, the monitor also including automatic control means and timing means for determining that data representing detected concentration of gas and data representing absence or presence of movement are recorded in correlation on a time basis as representing data obtained at the same times or over the same time periods at predetermined intervals, with the data recording means also recording and correlating such times or times associated with or representing said same time periods with the other data.

The automatic control means and timing means may be included in the data recording means and be an integral part thereof.

It will be understood that the data when retrieved or downloaded from the data recorder will provide the times of, or the times associated with the time periods of detecting the gas concentration values and the absence/presence of movement, and also the gas concentration values and 4 absence /presence indication detected at those times or over those time periods.

An important advantage of a monitor according to the invention is that an occupant of the premises being monitored does not have to keep a diary of the times of his/her occupancy of the room or area being monitored.

The information recorded by the recording means will provide a good indication of the times when the occupant was in the room or area (providing the occupant is not totally stationary) and the levels of gas that the occupant was exposed to at those time.

Preferably, the or each gas sensor is an electrochemical gas sensor, which operates in the absence of a pump. Known such kinds of suitable sensors are designed for low level measurements and are of a natural diffusion type, which eliminates the need for the sensors to have sampling pumps.

This provides the advantage of quiet operation.

The monitor may, for example, include three gas sensors, for detecting, say, nitrogen dioxide, carbon monoxide and oxygen, respectively.

The device for detecting movement may be an infra-red detector. Conveniently the occupancy detector may have a degree lens vision.

Optionally, the monitor may also include temperature measuring means and/or humidity measuring means, such means having data output means which communicate or connect with the data recording means whereby data representing measured temperature and/or measured humidity is input into and recorded by the data recording means, with the temperature measuring means and/or the humidity measuring means also being under the control of the automatic control means and timing means such that data representing temperature and/or humidity measurement is recorded by the data recorder in correlation on the same time basis at the same times, or over the same time periods, at the same predetermined intervals, as the other data recorded by the data recording means.

The data recording means may be a data logger.

The invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a front schematic view of one embodiment of monitor according to the invention; Figure 2 is a schematic view of the interior of the monitor; and 6 Figure 3 shows an example of a printout of a table collating together information downloaded from the data recording means.

Referring to Figure 1 of the drawings, a monitor 1 comprises a f ront panel 2. On the f ront panel 2 there are mounted three electrochemical gas sensors 3, 4 and 5. Sensor 3 is for sensing carbon monoxide, sensor 4 is for sensing nitrogen dioxide, and sensor 5 is for sensing oxygen. The electrochemical gas sensors enable low concentration levels of N02. CO and 02 to be sampled continually over a period of time. Also mounted on the front panel 2 are a temperature measuring device 6, a relative humidity measuring device 7 and an infra-red movement detecting device 8. The sensors 3, 4 and S, measuring devices 6 and 7 and movement detecting device 8 are of known kinds and produce electrical outputs as a result of performing their various functions.

An on-off switch 9 is also included on the front panel 2.

It will be understood by those skilled in the art that the gas sensors 3, 4 and 5, and the other devices 6, 7 and 8 may have to be calibrated according to the manufacturer's instructions.

In Figure 2, the three gas sensors 3, 4 and 5 and the inf ra red movement detecting device 8 have lines 10, 11, 12 and 13 7 f or carrying output data which pass via a circuitry board 14 to a data logger 15. The temperature measuring device 6 and the humidity measuring device 7 have lines 16 and 17, respectively, for carrying output data which are connected to the data logger 15. The data logger comprises associated programmable automatic control means 18 and timing means 19 (as is known to those skilled in the art of data loggers) for ensuring or determining that data is obtained from the sensors and the devices and recorded on a predetermined time basis. Times associated with the time periods over which the data is recorded by the logger 15 is also recorded by the logger.

The monitor is powered by a 12 volt battery 20 which enables the monitor to "run" continuously for several days. The battery is connected and supplies power to the data logger 15 by line 21 and the circuit board 14 by line 22. It will be appreciated that whilst only single "block diagram" connection lines are shown in Figure 2, the battery supplies power to the gas sensors 3, 4 and 5, to the devices 6, 7 and 8, and also to the switch 9, either via the data logger or the circuit board. It will of course be understood that the gas sensors 3, 4 and 5, and the devices 6, 7 and 8 have associated electrical circuitry not shown in the schematic block diagram of Figure 2. Where required it will be appreciated that in a normal manner the circuit board can be 8 arranged to provide circuit magnification to output signals from the sensors and devices.

A single switch 9 is used to switch on the data logger 15 and start the sampling of all the sensors and devices which are connected to the logger, simultaneously.

As all of the components of the monitor are small they can be assembled and connected together in a compact manner. For example, a monitor assembled by the applicants comprised a casing measuring aproximately 23cm in length, 26cm in width and 15cm in height.

The automatic control means 18 and timing means 19 associated with the data logger in this example was programmed, following manufacturer's guidelines on use, such that readings or measurements made or sampled by the three gas sensors 3, 4 and 5 and the three devices 6, 7 and 8 are sampled simultaneously and continually at one second intervals, with the respective sampled data readings being averaged over one minute time periods and being recorded as averaged data by the logger at one minute intervals.

Thus, data representing the values of the measurements sampled by the sensors and also the devices is recorded in the data logger against the common times associated with or 9 representing the time periods of such measurement at one minute intervals.

In the present example the data recorded or stored in the data logger is downloaded from the logger via logger communication cable 25 to a personal computer 26. From the personal computer a table can be printed and analysed in an appropriate data analysing package (as is known to those skilled in the art) which correlates a time (including date if required) and the various measurements obtained and averaged over common time periods at different times at regular time intervals. An example of a part of such a table is shown in Figure 3 listing against date and a time which in each case is the time associated with or indicating the start time of each one minute time period over which the measurements are obtained and averaged - humidity, temperature, personal motion (presence /absence of occupant's movement), and concentrations of nitrogen dioxide, oxygen and carbon dioxide. In this particular example, the movement detector (or passive motion sensor) produces readings of 11501, when no movement is detected and readings above 115011 when movement is detected.

In addition, the correlated data in the table clearly shows that for some of the time covered in the table elevated concentrations of nitrogen dioxide and carbon monoxide were present indicating that one or more persons were exposed to these concentrations in the area or room being monitored by the monitor.

It will be understood that in a different embodiment of monitor according to the invention, the data logger can be arranged to record data from the sensors and devices obtained at specific instants of time at predetermined time intervals rather than the data being averaged over periods of time, with data representing those instants of time also being recorded by the data logger.

It will be appreciated that the above described monitor enables monitoring of, say, a kitchen environment, on a time recorded basis by a quiet or virtually silent monitor which may be stood unobtrusively in a corner on a work surface without the occupant having to do anything, with the monitor also recording data for indicating whether or not the room is occupied.

Claims (9)

1. A gas monitor including at least one gas sensor for detecting the concentration of a gas, a device for detecting movement of a person within a predetermined area, and a data recording means, the gas sensor and movement detecting device having respective data output means which communicate or connect with the data recording means whereby data representing detected concentration of gas and data representing presence or absence of movement, respectively, is input into and recorded by the data recording means, the monitor also including automatic control means and timing means for determining that data representing detected concentration of gas and data representing absence or presence of movement are recorded in correlation on a time basis as representing data obtained at the same times or over the same time periods at predetermined intervals, with the data recording means also recording and correlating such times or times associated with or representing said same time periods with the other data.

2. A monitor as claimed in claim 1, including one or more further gas sensors, with each sensor dedicated to sense a different gas.

12

3. A monitor as claimed in claim 1 or 2, in which the or each sensor is an electrochemical gas sensor.

4. A monitor as claimed in any of the preceding claims, in which the movement detecting device is an infra-red sensor.

5. A monitor as claimed in claim 4, in which the infra-red detector has substantially 180" lens vision.

6. A monitor as claimed in any of the preceding claims, in which the data recording means is a data logger.

7. A monitor as claimed in any of the preceding claims, further including temperature measuring means having data output means which communicates or is connected with the data recording means whereby data representing measured temperature is input into and recorded by the data recording means, with the temperature measuring means also being under the control of the automatic control means and timing means such that the data representing the measured temperature is recorded in correlation on the same time basis at the same times or over the same time periods and predetermined intervals as the other data recorded by the data recording means.

8. A monitor as claimed in any of the preceding claims, further including a humidity measuring means having data 13 output means which communicates or is connected with the data recording means whereby data representing measured humidity is input into and recorded by the data recording means, with the humidity measuring means also being under the control of the automatic control means and timing means such that the data representing the measured humidity is recorded in correlation on the same time basis at the same times or over the same time periods and predetermined intervals as the other data recorded by the data recording means.

9. A gas monitor substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.