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Environmental Quality Corner with Ken Appel

FDA Compliance

Comparing Pharmaceutical Continuous Monitoring Systems: Part 2

Wired, wireless, and stand-alone monitoring instruments

Published: Tuesday, November 16, 2010 - 06:00

Ken Appel is the manager of regulated industries for Veriteq.

In part 1 of this article, we discussed the pros and cons of various systems for stand-alone monitoring instruments (e.g., chart recorders and data loggers) and wired networks, with and without power over Ethernet (POE). In the second part of this article, we will look at two types of wireless monitoring—Wi-Fi and mesh—and continue the discussion of the risk factors (figure 1) and costs of ownership (figure 2).


Click on image to enlarge.
Figure 1: General guidelines to risks associated with meeting good manufacturing practices (GMP) requirements


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Figure 2: General guidelines for some of the more salient factors affecting costs of ownership related to the six monitoring options. Varying plant sizes and scale of operations affect the impacts of various cost factors.

Wireless networks—WiFi and mesh

For many pharmaceutical plants, and especially those in older facilities where there are difficulties in running Ethernet cabling, wireless communications can be a convenient and cost-effective method of connectivity. Ease of installation, reduction in cabling cost, and the ability to measure in inaccessible areas are among the major factors driving the adoption of wireless networking.

Unlike the wired IEEE 802.3 international standard, several wireless communications protocols have emerged, including the popular wireless version of Ethernet, commonly referred to as “WiFi”—wireless fidelity—(IEEE 802.11b and more recently IEEE 802.11g). Other network methodologies used for monitoring include a mesh structure based on the ZigBee/IEEE 802.15.4 protocol (figure 3).

WiFi is often the wireless system of choice because it uses the same information technology (IT) infrastructure already in place in an organization. Wireless mesh (ZigBee) is a network architecture that uses access points or nodes to communicate with one another as well as with the host. It is designed to detect a degraded signal at one access point and reroute it to another nearby access point. Nodes have a low power requirement, which has the expectation of less drain on battery life, but at the same time, low power inherently means less signal strength than WiFi. The low power requirement of ZigBee networks also means that there must be a sufficient number of nodes to maintain continuous data flow.

Whether WiFi or wireless mesh, the greatest downside is the possibility for network interruptions, such as those that occur when lift trucks momentarily block a signal, or when inventory is rearranged, or equipment is moved out of range. These potential obstacles to wireless transmission can affect monitoring equipment’s ability to capture gap-free records. Fixed obstacles that could block the signal can be overcome using a sufficient number of wireless access devices. Intrusions from a forklift, storage equipment such as water-based gel packs, or office modifications may not be easy to anticipate or deal with.

Figure 3: Topology of WiFi and mesh wireless networks. WiFi devices connect directly to the company network and use WiFi access points to transmit data to a central host (server). Mesh devices connect to a gateway that can either host the data or forward to a central server.


The range for a wireless device is largely dependent on radio strength, which is also tied to the battery power. Installations using wireless monitoring technology have to accommodate signal range and barriers, which become important factors when continuous data are required. It can mean, for example, that more wireless devices are needed (and greater upfront cost) to ensure network transmission integrity in all situations.

With wireless mesh networks, signals are diverted to maintain data flow, but this increases the load on other nodes picking up the signal, which can influence battery life in unpredictable ways. These types of systems need a vigilant source for detecting and alerting for low-battery issues well before data are lost.

With wireless systems, signals carrying critical data can also degrade from interfering sources such as other devices communicating in the same 2.4 GHz band (many WiFi and ZigBee devices operate in this range, although other frequency are opening up), and in today’s pharmaceutical plants, this can include security cameras, microwave ovens, and Bluetooth devices. Wireless mesh is a proprietary network that needs to be integrated with the various standards used in the existing infrastructure—involving IT hours, which potentially impacts costs of ownership.

The batteries used in wireless devices are specified with “up to” so many months or years of life. The “up to” condition is often stated for ideal or laboratory conditions. This is because there are no typical operating conditions where power consumption can be calculated. Devices draw down battery power with each transmission, which includes the frequency of measurement updates established by the user, as well as by events such as alarms or communication problems brought on by many circumstances, including a blocked access device. Battery drain is even less predictable in a mesh infrastructure. For example, when the signal between a temperature device and node is blocked, another nearby node picks up the signal for transmission. It now adds the new transmissions to those from other measurement devices it was already communicating with. The extent to which a wireless network requires battery replacements reintroduces human error potentials into what are assumed to be relatively error-proof automated systems.

Most connectivity methods have low risk of losing data when the time between real-time updates for data and alarms is long. For example, the initial requirements of a monitoring system may not have needed frequent data updates, but at some point someone may want to know if a chamber door was left open or other behavior that led up to a temperature excursion. In these instances, a faster sample rate would be needed, requiring more transmissions and thus making more demands on the battery. Reduced battery life is well and good if standard operating procedures (SOPs) can anticipate the need, staff has the time for required maintenance without fail, and the expense of more frequent service (from labor hours and replacements) are not burdensome. Some devices provide low-battery indicators and alarms. However, what happens to data if batteries are not replaced in time? Moreover, it is highly probable that data will be lost in systems that use the same batteries to power both the wireless radio and data-memory electronics. Battery life therefore is not a minor specification but, in fact, has great effect on the ability to ensure compliant, gap-free records and minimize the effects of human error on quality assurance systems.

Data redundancy

Whether deploying a system of stand-alone devices, or a wired or wireless network for monitoring critical environments, the need for a continuous record of data and events are the same. There will be times when the facility experiences network, power, or other types of interruptions. Assuming the need for a continuous quality record, the monitoring system should be capable of filling in a database when temperature, relative humidity, pressure, and other data cannot be communicated in real time. This is nearly impossible and impractical with stand-alone monitoring instruments, making them obsolete technology.

In networked systems, recording data independently at the point of measurement is one key factor in protecting data. A system capable of identifying the time period of a communication interruption and bringing in data and events to fill the gap is essential to ensuring complete and accessible records. This assumes measurement devices have calibrated time-base clocks (specified with an accuracy over a temperature range) to ensure correct time and data recording. The capability to back-fill data after power or network interruptions ensures a continuous record of data and events. Completeness of records also assumes there is an audit trail to capture all system events. Documented evidence of data and events during an outage will reduce quality management’s involvement in reviewing excursions and investigating deviations. Gap-free records save time during and after an audit, reduce unnecessary staff involvement, and limit disruptions to ongoing production and shipments.

Data security

There are two aspects of security that the U.S. Food and Drug Administration’s (FDA) 21 CFR Part 11 rule requires: protecting data from unauthorized access and preventing alteration to data. Secure data begins at the measurement device and ends at a designated collection point, usually a network server. Secure access refers to specific levels of permission given to authorized users, and other protocols for ensuring authenticity.

Devices communicate using protocols or common rules for data format and can be either open (public) or proprietary. An open protocol means just that: Anyone who knows the rules can potentially access the files. A secure monitoring system ensures that the measurement device has a secure protocol in addition to other authentication and confidentiality features. This is a major factor in how and why communicating over wire is inherently more secure. In wired systems devices are only accessible within the building. A wired network can potentially be compromised only by someone who has already gained access to the facility.

On the other hand, wireless communications is inherently less secure and requires additional measures to maintain protections. Wireless devices are also manufactured with security features built in but may not be upgradable to the changing standards or security requirements of an organization. A capital investment made now may need to be made again in two years. Nonstandard, proprietary wireless networks require IT training and may be at increased risk due to IT staff turnover.

Conclusion: quantify risk and cost

Whether you use stand-alone monitoring instruments, or wired or wireless connectivity for your temperature and humidity measurement devices, it is important to understand the limitations of each method. For the most part, the significant labor costs involved in stand-alone monitoring devices combined with the multiple ways in which such systems insert human error potential make them less than desirable compared to more automated network-based monitoring technology.

Wireless communication has the advantages of being flexible to install and for providing monitoring of environments that have limited access to running cable or where refrigerators, freezers, or other monitored storage units are moved on a frequent basis. Wired networks have the advantage of speed, security, and data redundancy. Generally speaking, if your goal is to reduce the risk of data loss to zero or nearly so, then wired systems are the best course. The lower upfront cost of wireless can disappear quickly if you have to write deviation reports due to missing data, product loss, or regulatory missteps. The good news is that connectivity technologies can be mixed—wired and wireless—solving the physical installation challenges that many facilities pose.

Of course network connectivity methods alone do not maintain product quality. They have to be used in conjunction with the capabilities of the facility’s monitoring system, with specific attention to automating records—such as data, events, and audit trails—that present a continuous gap-free history.

The details of how humans interact with systems—whether driving lift trucks, replacing batteries, or downloading data—are important factors in determining if a particular continuous-monitoring technology truly minimizes risks introduced by the inevitability of human error. You have to weigh the costs of potential problems vs. how much your organization is willing to invest to protect your operations.

Risk really comes down to consequences or the implications of system failure. Analysis of risk is both qualitative and quantitative. Ideally, you should be able to answer the following questions:

• Can you afford to handle the expense of downtime? This can be in the form of missing data, equipment failure, or human error.
• For an unplanned production stoppage, how long will it affect other research, production, or shipments?
• What is the financial effect of losing product or research specimens?
• Can you define downtime cost either by time, lost production, blemish to reputation, or other stakeholder pain?
• Can you identify single points of failure and ways to reduce them?
• Does it cost more to recover from equipment failure, product loss, internal and external reviews, and other unplanned interruptions than it would to invest in continuous operation?


About The Author

Environmental Quality Corner with Ken Appel’s picture

Environmental Quality Corner with Ken Appel

Ken Appel, author of Quality Digest’s Environmental Quality Corner, is manager regulated markets for Veriteq, a Vaisala company. Veriteq provides environmental monitoring of temperature, humidity and other critical variables in controlled environments for regulated industries and other critical storage applications where product loss or audit failures are unacceptable.