GB2624227A

GB2624227A - Time weighted gas detector

Info

Publication number: GB2624227A
Application number: GB2216863.7A
Authority: GB
Inventors: Summerfield Adrian
Original assignee: Crowcon Detection Instruments Ltd
Current assignee: Crowcon Detection Instruments Ltd
Priority date: 2022-11-11
Filing date: 2022-11-11
Publication date: 2024-05-15
Also published as: GB202216863D0

Abstract

A method for measuring exposure data to a target gas using a gas detector configured to detect the presence of the gas; operating the gas detector in a first state: detecting concentration of the gas, recording first exposure data to the gas, storing the first exposure data in a memory, and determining a time weighted average value based on the first exposure data; switching the gas detector from the first state to a second state based on an input, in response to switching the detector to the second state: detecting concentration of the gas and recording second exposure data; returning the gas detector to the first state based on an input, and in response thereto: retrieving the first exposure data from memory and continuing recording the first exposure data, and updating the time weighted average value based on the first exposure data and not the second exposure data.

Description

Time Weighted Gas Detector

TECHNICAL FIELD

The present disclosure relates to a device and method for measuring a response to a first target gas. Particularly, but not exclusively, it relates to a gas detector for measuring exposure data over an extended period of time.

BACKGROUND

Typically, gas detectors are operated to measure the presence of potentially dangerous gases to determine an exposure level of the user. This is done to ensure that workers are not exposed to a dangerous level of gas during a set period of time such as a work shift. Existing solutions measure exposure data and continually add this data to a time weighted average value to determine the exposure level. A time weighted average value is used where a user may be exposed to varying levels of gases over varying time periods.

The exposure of a user to a target gas can also be defined as a Short Term Exposure Level (STEL) or Long Term Exposure Level (LTEL). The STEL is often defined as the acceptable exposure to a target gas over a period of time, typically 15 to 30 minutes, as long as the time average exposure over the period of time is not exceeded. The LTEL defines the acceptable exposure to a target gas over a long period of time, typically 8 hours. STEL and LTEL values are typically set by government bodies and must be adhered to in order to ensure the safety of During operation of the gas detector, it is common for the user to perform different tests such as a confined space entry test or to work in different environments which may require the use of personal protection equipment (PPE). In a confined space entry check, the user themselves is not exposed to the gas but rather an extending tube attached to the gas detector may be used. Similarly, in an environment where the user is wearing PPE such as breathing apparatus, for example, the user is not exposed to the gas.

Accordingly, the ability to improve the accuracy of exposure level measurements is desirable.

An object of the present invention is to mitigate some of the deficiencies of the prior art mentioned above.

SUMMARY OF THE INVENTION

Aspects and embodiments of the invention provide an improved method and device which enable a user of a gas detector to continuously record exposure data over the course of a work day, for example, whilst only accruing data towards their time weighted average value in certain situations. Such situations are those in which the user themselves are actually exposed to target gases and do not include those situations where the device is exposed but the user themselves is not (for example, the user is wearing protective equipment). This allows for the more accurate determination of the time weighted average value whilst requiring minimal input from the user. The accurate recording of user exposure reduces the risk of overexposure.

According to an aspect of the invention there is provided a method for measuring exposure data to a target gas using a gas detector, wherein the gas detector comprises a gas sensor configured to detect the presence of the target gas. Said gas sensor in communication with a processor and a memory, wherein the method comprises: when the gas detector is in a first state: detecting, using the gas sensor, a presence of the target gas; recording first exposure data to the target gas; storing the first exposure data in the memory; and determining a time weighted average value based on the first exposure data. The method further comprises switching the gas detector from the first state to a second state. In response to switching the gas detector to the second state: detecting, using the gas sensor, a presence of the target gas; and recording second exposure data to the target gas. The gas detector is then returned to the first state; and in response to returning the gas detector to the first state: continuing recording the first exposure data; and updating the time weighted average value based on the first exposure data and not the second exposure data.

Optionally the method further comprising determining that a threshold period of time has elapsed before continuing recording the first exposure data and updating the time weighted average value. In some instances, the threshold period of time is between 10 seconds and 30 seconds. This ensures that the exposure data used in the calculation of the time weighted average value is correct and does not include any data which may be from residual gases in the second state.

Optionally wherein the gas detector switches between the first and second state as a result of user input. In some examples, the user input is a touch based input.

Further, wherein the user input is made in response to a user prompt. This indicates that the gas detector is awaiting input and reminds the user to select the appropriate state of the detector.

Optionally wherein switching the gas detector to the second state comprises initiating a test in a test mode. Optionally wherein returning the gas detector to the first state comprises returning the gas detector to the first state automatically in response to completing the test in the test mode. The test may be a confined space entry check. This reduces user input after completing a test as the device is automatically transitioned to the first state.

Optionally wherein the time weighted average is a measure of a user's level of exposure over a given time period.

Optionally the method further comprising displaying the first exposure data and/or the second exposure data to a user. This allows the user easy access to important information throughout the work shift.

Optionally the method further comprising transmitting the first exposure data and/or the second exposure data to an external location. This allows exposure data to be monitored remotely.

There is also provided a gas detector for measuring exposure data to a target gas, the gas detector comprising a gas sensor configured to detect the presence of the target gas, said gas sensor in communication with a processor and a memory, wherein the gas detector has: a first state in which the gas sensor detects the concentration of the target gas, and records and stores first exposure data in the memory, wherein the first exposure data is used to determine a time weighted average value, and a second state in which the gas sensor detects the concentration of the target gas, and records second exposure data, wherein the second exposure data is not used to determine the time weighted average value. Wherein the gas detector is configured to selectively switch between the first state and the second state; and the gas detector has an input sensor configured to receive at least one input, and dependant on the input received, retrieve the first exposure data from memory.

There is also provided a system comprising one or more detectors and further comprising a central server, wherein one or more of the detectors are configured to communicate with the central server.

There is also provided a computer program product comprising instructions which, when the program is executed by a computer, cause the computer to carry out any of the above recited method steps.

Within the scope of this application, it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible.

The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAVVINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic representation of the apparatus according to an aspect of the invention; Figure 2 is a flow chart of the process of operating the gas detector apparatus in a first and second state according to an aspect of the invention; Figure 3 is a flow chart of the process of switching the gas detector between first and second states according to an aspect of the invention; and Figure 4 is a flow chart of the process of operating the gas detector apparatus in a test mode according to an aspect of the invention.

DETAILED DESCRIPTION

The present invention provides a device and method capable of continually recording exposure data whilst only determining a time weighted average value of a user based on exposure data where the user was actually exposed to one or more gases. Such a gas detector 10 is shown in Figure 1 in accordance with the claimed invention.

Figure 1 shows a schematic of a gas detector 10. The gas detector 10 comprises at least a housing 11 in which there is at least a gas sensor 15, a processor 20, a memory 25, and an input sensor in the form of a user input means 30 and/or a motion detection means 32. The input sensor in an embodiment comprises signal receiving means 33, with a signal being generated externally and broadcast to the gas detector 10.

The housing 11 is rugged housing in which is placed the gas sensor 15, a processor 20, a memory 25 and an input sensor in the form of either a user input means 30 and/or a motion detection means 32 and/or signal receiving means 33. The gas sensor 15 is a known gas sensor and configured to the presence and preferably the concentration of one or more target gases. The processor 20 is configured to receive data from the gas sensor 15 and from the data the processor is configured to produce exposure data to the target gas. The processor 20 produces the exposure data from the gas sensor 15 data in a known manner.

The detector further comprises a form of memory, preferably non-volatile memory, and the processor 20 is configured to write data, such as the calculated exposure data to the memory 25. The memory 25 is capable of storing data when the gas detector is deactivated.

In one embodiment, the gas detector 10 comprises a user input means 30. The user input means in an embodiment is an actuation means, for example, a button. In further embodiments the user input means 30 is an alphanumeric keypad, or touchscreen, with which the user may input one or more commands. The user input means 30 may be any known suitable means for enabling a user to input a command to the detector 10.

In an alternative embodiment, the gas detector 10 comprises a motion detection means 32. The motion detection means 32 in an embodiment is an accelerometer and/or gyroscope. In further embodiments the motion detection means 32 comprises a known Global Positioning System, GPS, unit, and the processor 20 is configured to query the GPS unit at regular intervals in order to determine the position of the unit. From such data any motion and resulting displacement of the device may be determined. As such any suitable means for determining whether the detector 10 has moved i.e., has been displaced, and/or is in motion may be used.

It will be apparent to the skilled person that within the context of the invention, the terms 'motion', 'movement' and 'displacement' may be taken as interchangeable.

In an alternative embodiment, the gas detector 10 comprises signal receiving means 33. The signal receiving means 33 in an embodiment is a known radio antenna for receiving transmitted commands from a remote transmitter. In further embodiments the signal receiving means comprises any known suitable means for receiving a transmission.

In a further embodiment, the gas detector 10 comprises a combination of user input means 30, a motion detection means 32 and a signal receiving means 33.

Optionally, the gas detector 10 comprises a display 35 allowing exposure data to be communicated to a user. This display 35 may be a liquid-crystal display, LCD, screen, for example, or any other known suitable means of display such as a touchscreen display. The display 35 is preferably active during operation of the device in the first state and/or in the second state.

Optionally, the gas detector 10 comprises a transmitter 40 allowing exposure data to be transmitted to an external location. The transmitter 40 in an embodiment is a known radio transmitter. In further embodiments other known suitable means of data transmission are used. The transmission of the exposure data is configured to occur as the exposure data is calculated or at regular intervals of time so as to enable real time recording of the user's data. In further embodiments transmission of the data occurs when the gas detector 10 switches between the first state and the second state.

In use of the detector 10, the processor 20 produces the exposure data from the gas sensor 15 data in a known manner. The exposure data is written to the memory 25. When the detector is powered up, the processor is further configured to detect for the presence of an input indicating which state the detector 10 is to operate in.

Alternatively, the detector 10 may automatically operate in a first state in response to being powered up. When the detector 10 is operated in the first state, exposure data stored in memory may be retrieved and used in subsequent calculations if the stored data is within a certain time period. If the stored exposure data is used then a cumulative exposure to the gas is calculated using the previously stored/recorded value.

In use the user may input to the detector, via the user input means 30, that the device is to operate in the first state. Such an input may be made by pressing a button, inputting via a menu etc. The user may utilise the input means 30 when utilising the detector 10 for the first time (e.g., after taking the device from another user) or whenever the situation dictates. Thus the user is able to selectively switch between the first and second state according to their usage needs. This is described in further details with reference to Figures 2, 3 and 4.

In use the signal receiving means 33 are configured to receive a command transmitted from a remote location. A central control station may utilise the signal receiving means 33 for enabling the recording of accurate exposure data or broadcast a signal to mark the end of a work shift. Such a signal can be transmitted to multiple gas detectors 10.

The ability of the gas detector 10 to operate between a first state where exposure data can be stored and retrieved to be used in accruing data towards a time weighted average value and a second state where exposure data is recorded but not used in calculating the time weighted average value allows the detector 10 to more accurately determine the exposure to a target gas across a period of time that may include one or more instances of a user working in a situation where they themselves are not exposed to one or more target gases. This leads to more accurate data being available to the user. Moreover, the ability of the gas detector to determine to retrieve the exposure data from memory when in the first state reduces the possibility of data loss as a result of user error and reduces reliance on any supplementary hardware or control systems outside of the gas detector itself.

This helps ensure the reliability of the system whilst at the same time reducing costs.

Figure 2 is a flow chart of the process of operating a gas detector, such as detector 10, according to an aspect of the invention.

At step 5200, the gas sensor 15 detects the presence of a gas, and more specifically, is able to detect the concentration of the target gas. The processor 20 then uses the detection to record first exposure data at step 5202. The first exposure data can be indicative of the concentration of the target gas over a certain time period.

The processor 20 uses the recorded exposure data to determine a time weighted average value (TWA) at step 5204. A time weighted average value is a term used in workplace safety and is indicative of a user's accumulative exposure to hazardous substances over a period of time. It is calculated as the sum of the levels of the target gas multiplied by the portions of time the user was exposed to the corresponding level and is averaged to different time periods depending on the user's schedule. Typically, the value may be averaged to an 8-hour workday or a 40-hour work week. An example is shown below in equation (1).

+ T2L2 + * * + TnLn TW A - (1) number of hours Where Tn is a period of time (such as 0.5 hours), Ln is the level of target gas the user was exposed to during that period of time, and the number of hours refers to the total period of time (such as an 8 hour work day).

During the course of a user's day, the user may wish to complete different tasks using the gas detector 10 where the gas detector 10 is exposed to target gases but the user themselves is not. As the user is not exposed to the target gas the readings taken during the task where the user is not exposed to the target gas should not contribute to the user's TWA value. For example, the user may enter an environment containing target gases and wear respirator equipment. In this case, the user is protected from the target gases and thus any exposure reading while wearing the respirator equipment should not contribute to their TWA value.

Similarly, exposure data during a confined space entry check, for example, should not contribute to the TWA value. This is described in more detail with respect to Figure 4.

Beneficially, the invention enables the detector 10 to work in a second mode at step 5206 for cases such as the examples above. The second state can be entered in response to a user input indicating to enter the second state or may be in response to the user initiating a test mode. In the second mode, the detector 10 detects gas at step 5208 and records second exposure data at step 5210. Contrary to in the first mode, in the second mode the second exposure data is not used for the TWA value determination as indicated at step 5212 of Figure 2. This enables the gas detector 10 to still measure and record data in the environment whilst not adding this data to the determination of the TWA value. This is important for the user's safety as there may be leaks outside of the area in which protection is worn such that the gas detector alarms should still be operational and recording data.

The user can selectively switch the detector 10 between the two states of operation multiple times during the day as required.

Figure 3 is a flow chart of the process of operating a gas detector, such as detector 10, according to an aspect of the invention. Steps S200 to 5212 in Figure 3 are the same as the steps described in relation to Figure 2. The additional steps 5314 to 5320 are discussed in detail below.

After recording data in the second mode, a user may wish to return to the first mode. For example, the user have had to use breathing apparatus for a period of tme and has subsequently remove their breathing apparatus or may complete a test such that exposure readings should once again contribute to their TWA value. Therefore, at step 5314 of Figure 3, the device can enter into the first mode, detect gas at step 5316, and record first exposure data again at step 5318. This first exposure data can be used to update, at step 5320, the TWA value that was determined at step 5204. Thus, the TWA value can be retrieved from memory and updated during the course of operation whilst in the first mode. Advantageously, this enables the TWA value of the user to be accurately calculated for extended periods of time where certain periods of time are excluded from the calculation.

Further, the ability for the detector 10 to switch between accruing data towards the TWA value and not accruing data towards the TWA value requires minimal user input.

In some examples, the user input may be provided as a result of receiving a user prompt or reminder from the detector 10 suggesting that the user may wish to transition to another mode. Such a prompt may be issued after a threshold period of time of operating in a single mode. For example, a prompt may be issued after a user has operated in the second state for more than 25 minutes. The prompt may also be issued at regular intervals. This helps, for example, to ensure that the user does not forget to return the detector 10 to the original state once they have finished a test. This can ensure that the TWA value is accurately determined.

The gas detector may comprise an override step in which the exposure data stored in memory 25 is discarded after a period of time sufficient for a user's shift to have ended. In this way, the first exposure data and the determination of the TWA value can be restarted for each work shift automatically.

Figure 4 is a flow chart of the process of operating a gas detector, such as detector 10, during a test mode according to an aspect of the invention. The embodiment of Figure 4 is a specific use case useful for understanding the invention. Other implementations, and use cases, are possible.

At step S400 of Figure 4, the device enters a test mode. For example, one test may be a confined space entry test. As mentioned above, a user of the gas detector 10 will typically carry out confined space entry checks where the user uses the detector 10 in combination with an extension, such as a tube, which is placed in the confined space to test the exposure level of the confined space before entering the confined space themselves. Here, the TWA value should not be altered whilst such tests are carried out as the user is not exposed to the gases in the confined space.

At step 5402, the detector 10 detects the gas and records the test exposure data at step 5404. The user then completes the test and exits the test mode on the detector 10 at step S406. The user may indicate completion of the test by a user input on the detector 10 such as a button press.

On completing the test, the device may automatically wait a threshold period of time at step 5408 before recording first exposure data at step S410. Step S408 is an optional step as indicated by the dashed lines. It is beneficial to wait a threshold period of time as some residual gas may still be detected after removing the extension from the confined space and exiting the test mode. Typically, such residual gases will decay in about 10 to 30 seconds. The time taken for a gas to decay by 90% is known as the T90 time and will vary according to the type of gas being detected. Preferably, the threshold period of time is between 10 and 30 seconds and optionally determined by the T90 time of the target gas. Some detectors 10 may operate with a 30 second delay whilst some detectors 10 may operate with a 10 second delay.

After exiting the test mode at step 5406 or, optionally, after waiting a threshold period of time at step S408, the detector 10 continues to record first exposure data at step 5410. This first exposure data is used to determine a time weighted average value at step 5412. The test exposure data is not used in this determination. In this example, the detector 10 can transition back to the first mode which contributes to the TWA value automatically in response to completing the test. No additional user input may be required.

The approaches described herein provide for an effective method and device for determining a time weighted average value of a user which accurately reflects the user's exposure levels during a specified time period. Such an approach allows user's to quickly and efficiently operate a single gas detector in different modes which may or may not contribute to the TWA value. Further, the user's safety is increased by more reliably determining an accurate TWA value.

Claims

Claims 1. A method for measuring exposure data to a target gas using a gas detector, wherein the gas detector comprises a gas sensor configured to detect a presence of the target gas, said gas sensor in communication with a processor and a memory, wherein the method comprises: when the gas detector is in a first state: detecting, using the gas sensor, a presence of the target gas; recording first exposure data to the target gas; storing the first exposure data in the memory; and determining a time weighted average value based on the first exposure data; switching the gas detector from the first state to a second state; in response to switching the gas detector to the second state: detecting, using the gas sensor, a presence of the target gas; and recording second exposure data to the target gas; returning the gas detector to the first state; and in response to returning the gas detector to the first state: continuing recording the first exposure data; and updating the time weighted average value based on the first exposure data and not the second exposure data.
2. The method of any preceding claim, further comprising determining that a threshold period of time has elapsed before continuing recording the first exposure data and updating the time weighted average value.
3. The method of claim 2, wherein the threshold period of time is between 10 seconds and 30 seconds.
4. The method of any preceding claim, wherein the gas detector switches between the first and second state as a result of user input.
5. The method of claim 4, wherein the user input is a touch based input.
6. The method of any of claims 4 to 5, wherein the user input is made in response to a user prompt.
7. The method of any preceding claim, wherein switching the gas detector to the second state comprises initiating a test in a test mode.
8. The method of claim 7, wherein returning the gas detector to the first state comprises returning the gas detector to the first state automatically in response to completing the test in the test mode.
9. The method of any of claims 7 to 8, wherein the test is a confined space entry check.
10.The method of any preceding claim, wherein the time weighted average is a measure of a user's level of exposure over a given time period.
11.The method of any preceding claim, further comprising displaying the first exposure data and/or the second exposure data to a user.
12.The method of any preceding claim, further comprising transmitting the first exposure data and/or the second exposure data to an external location.
13.A gas detector for measuring exposure data to a target gas, the gas detector comprising a gas sensor configured to detect a presence of the target gas, said gas sensor in communication with a processor and a memory, wherein the gas detector has: a first state in which the gas sensor detects a concentration of the target gas, and records and stores first exposure data in the memory, wherein the first exposure data is used to determine a time weighted average value, and a second state in which the gas sensor detects a concentration of the target gas, and records second exposure data, wherein the second exposure data is not used to determine the time weighted average value, wherein the gas detector is configured to selectively switch between the first state and the second state; and the gas detector has an input sensor configured to receive at least one input, and dependant on the input received, retrieve the first exposure data from memory.
14.A system comprising one or more detectors according to claim 13, and further comprising a central server, wherein one or more of the detectors are configured to communicate with the central server.
15.A computer program product comprising instructions which, when the program is executed by a computer, cause the computer to carry out any of claims 1 to 12.