E006: Temperature Monitoring Devices

The products in this category include thermometers, freeze indicators, temperature recorders, data loggers and event loggers for monitoring temperatures at all levels in the cold chain, including alarm systems.

Details regarding the products included in each sub-category of E006, as well as guidelines, performance specifications and verification protocols for this category, can be accessed through the drop-down sections below.

E006.1: Electronic Monitoring Systems

WHO IMD-PQS developed specifications for Electronic Monitoring Systems (EMS) in response to challenges and opportunities observed with existing monitoring systems. Data from existing monitoring devices were difficult to integrate into logistics management information systems (LMIC), due to a lack of standardization and inconsistent local access. Furthermore, there was limited guidance on data ownership and delivery protocols between systems.

To address these concerns, the goals of EMS are to enable standardization and interoperable data collection from cold chain equipment (CCE). The specifications require collection of performance and diagnostics parametres such as door openings , error codes, power availability, and compressor runtime to improve the value over just storage chamber temperature measurements. A history of these data must be stored in the CCE and made available for local access. A Machine to Machine (M2M) interface provides for plug-and-play upgradability of data display and remote data access.

E006.1.2 - EMS device functionality

The EMS specification set enables three levels of increasing functionality:

E006.1.2.1 - Level 1 Basic local data logging with USB data access

Data logger functionality makes the CCE the data repository for a consistent set of performance and indentification data elements. The data logger is integrated into the CCE, where it measures performance data and stores it in non-volatile memory for at least one year. The data include temperature, power availability, door openings, compressor runtime, equipment identification, and error codes. A USB port is provided to enable data access by computers, mobile phones, or other EMS-compliant devices, in both a standardized raw format and as a portable document format (PDF) human readable report.

The motivation for providing local data access is so that a service technician can access a history of the CCE's performance, even if the unit is unpowered, to aid in the diagnosing performance issues. In additiona, a machine-to-machine (MSM) interface consisting of the USB port and a power output port allows equipment monitoring devices (EMDs) to access the data for display and transmission purposes. Note that Level 1 does not require a visual display.

Beginning in 2024 with new E003 category products, all CCE must include a least this minimum level of functionality to be IMD-PQS prequalified. CCE with this functionality must meet WHO/PQS/E006/DL01.1 and be tested to WHO/PQS/E006/DL01-VP.1, or future revisions of those standards.

E006.1.2.2 - Level 2 Advanced local monitoring

Level 2 functionality includes the logging and data access capabilities of Level 1, and adds a local data display that allows healthcare workers of service technicians to monitor performance without needing to download data to a separate computer or smartphone. Visual and audible alarms prompt action from local users when urgently needed.

Suppliers may add advanced local displays and alerting by prequalifying as a "Local EMD" within the WHO/PQS/E006/EM01.1 specification and testing to WHO/PQS/E006/EM01-VP.1. It is anticipated that some CCE will have internal EMDs, and that manufacturers will also create external EMDs to be used with existing EMS-enabled CCE containing just data logging capability. These external EMDs use the M2M interface to access CCE data and obtain power. When the EMD is internal to an applicance, Level 1 Data Logger and M2M interface requirements must also be verified.

E006.1.2.3 - Level 3 Remote and local monitoring

Level 3 includes the capabilities of Level 2 and adds remote data transmission. This functionality allows service technicians to access data remotely and diagnose problems prior to a site visit. SMS or email alarms prompt remote users when something is amiss. The data also an be automatically routed to dashboards of future eLMIS systems to be available for aggregated visualization or reporting.

Suppliers may include remote data transmission by prequalifying as a "Remote EMD' within WHO/PQS/E006/EM01.1 and WHO/PQS/E006/EM011-VP.1. Level 2 functionality must also be verified, and if integrated within the CCE, Level 1 must be verified as well.

E006.1.3 - Further information about M2M interface and data files

A key aspect of Logger functionality is the "Machine-to-Machine" interface. This interface enables interoperability and upgradeability as monitoring technologies evolve. CCE with higher levels of EMS functionality (display + cellular connection) must still have this M2M interface.

The M2M interface consists of two parts:

1. USB Data interface

USB-C receptacle.
Presents as a USB mass storage device (like a USB drive).
Read-only, but no password protection permitted.
Data files in JSON format and a human-readable PDF report located in root directory.
Must operate even if CCE has no external power and monitoring battery is discharged, drawing power from the USB host device (external EMD, phone, or computer).

2. Barrel plug power output to power external EMDs

5 V output whenever appliance is powered.
Standard 2.1mm inside diameter / 5.5mm outside diameter size.
1.1 A current limit.

Further information related to the root directory file types and filename formats is available in the PQS Equipment Monitoring Systems (EMS) Introduction document.

E006.2: Other E006 device types

A number of different temperature monitoring device types are specified by PQS based on their particular applications in the cold chain. These range from more basic indicator and thermometers to advanced monitoring and communication systems. Employers of temperature monitoring should be familiar with the use-cases for the different types of devices and when best to deploy each type based on their specific programme needs and strategies.

E006.1.1: Alarms

Acoustic and visual alarms: These can be used in conjunction with fixed dial thermometers and pen recorders.

E006.1.2: Indicators

Cold Chain Monitor cards (CCM): WHO no longer recommends the use of these cards for in-country use. Their use should now be confined to international shipments only where dry ice is used. For more information and guidance on the use of CCMs, consult the WHO How to monitor temperature in the vaccine supply chain.

Freeze indicators: Freeze indicators should be used routinely for internal distribution of freeze-sensitive vaccines and for monitoring freezing events in cold rooms and vaccine refrigerators where alternative devices are not fitted, or are not thought to be reliable.

Vaccine vial monitors (VVM): VVMs or combined VVM/Threshold indicators are now routinely fixed to all vaccines supplied by UNICEF.

E006.1.3: Thermometers (no recording)

Electronic thermometers: Hand-held electronic thermometers are used by cold chain technicians during repair work, for routine monitoring, for cold chain studies and during the commissioning of cold rooms and freezer rooms.

Fixed dial thermometers: Fixed gas or vapor pressure dial thermometers require no power supply and they can be used to trigger an alarm system. Their primary use is as a back-up device for cold rooms and freezer rooms. Bi-metallic dial thermometers are no longer recommended because they easily lose their calibration.

Stem thermometers: A stem thermometer can be fitted in refrigerators, freezers, cold rooms and freezer rooms as an inexpensive back-up device for required 30-day temperature loggers. Stem thermometers should never be used as the primary temperature monitoring device because they do not provide a continuous record of vaccine temperature exposure. Bi-metallic dial thermometers are no longer recommended by WHO because they do not maintain their calibration.

Integrated electronic thermometer with alarm: This is a new device type which may be built-in to a vaccine refrigerator or freezer at the manufacturer’s discretion. Its purpose is to provide some of the capabilities of the monitoring equipment used on cold rooms and freezer rooms. This is the only E006 product type of which there are currently no examples on the market.

E006.1.4: Temperature recorders

Programmable remote temperature and event monitoring systems: Event monitoring systems consist of a network of sensors linked to a central temperature recording unit, which may connect and communicate with local and remote servers and services. Both hard-wired and wireless devices are available and devices of both types have integrated alarm systems. Detailed temperature records can be produced and the most sophisticated systems can be internet-enabled which allows for remote monitoring.

Pen recorders: Pen recorders have been standard equipment for cold rooms and freezer rooms for many years. They continue to have a use for smaller cold rooms and for programmes which are unable to provide the technical support needed to operate and maintain an event monitoring system.

Temperature data loggers: Data loggers are used principally during cold chain studies and for verifying performance during the initial commissioning of cold rooms and freezer rooms. Temperature data loggers have limited functionality. More advanced features can be found in 30-day electronic refrigerator temperature loggers.

30-day electronic refrigerator temperature loggers: All refrigerators must come equipped with a 30-day temperature logger device in compliance with WHO PQS standards. This device type can be used to review vaccine refrigerator temperatures over 30 days. The earliest data points are continuously overwritten so that the user always has access to the most recent 30-day period. The devices include a visual temperature alarm and some models allow data to be downloaded to a computer. Their use offers the possibility of much improved temperature monitoring at the health facility and lower sub-national levels where routine manual recording is known to be unreliable.

30-day temperature loggers are NOT suitable for use in vaccine freezers; see the WHO Vaccine Management Handbook for appropriate temperature logger devices for freezers.

Current models operate for two years after activation. The whole unit has to be replaced when the battery runs out because the product is supplied with sealed in batteries. This design approach avoids the need to recalibrate the device, which is expensive and logistically complex.

Electronic shipping indicators: Electronic shipping indicators are single-use devices designed to monitor vaccine temperature during international shipment from the manufacturer to the primary store. The data they provide is recorded on the Vaccine Arrival Report (VAR).

E006.3: Use of non-EMS E006 devices

The following table summarizes the use of each of the non-EMS E006 device types:

Table 1: Use of temperature monitoring devices

Note: The table shows the appropriate locations for each type of device. It does not imply that ALL the devices listed for a particular location should be used at the same time.