In the stability storage industry, it’s crucial that storage conditions can be guaranteed. Although controlled environments, if well-built, are designed to provide good air flow for uniformity of conditions like temperature and humidity, fluctuations and so-called hot and cold spots are not always avoidable. Identification of these during qualification means that any risk to stored materials from a condition excursion can be greatly reduced. It’s therefore imperative to ensure mapping is performed such that it provides representative data and ultimately confidence in your storage environment.
Step 1 – Know When Mapping is Required
Firstly, it’s important to know when you should be mapping. Remember that it’s not just a requirement of installation but should be repeated routinely and following any event that may impact how conditions are controlled and maintained. The five key ‘whens’ are as follows:
IQ/OQComprehensive mapping should be performed as part of any storage validation activity. This is the first time you will determine the uniformity of conditions across the environment and whether the controls for the environment require any adjustment. Consider the ‘states’ of mapping, as described in Step 2, based on how you intend to use the storage environment and what capacities of storage you will operate at.
Routine Re-QualificationControlled environments should be routinely re-qualified to highlight any potential changes across the environment extremes that may not be evident through routine monitoring. There’s no defined frequency for routine re-mapping but this should be based on the size of the environment and its potential to change over time. An industry typical re-qualification period is biennially.
Re-qualification following Planned MaintenanceWhere planned maintenance activities may impact the internal conditions of an environment; re-qualification should be performed as part of this activity. For example, following an annual de-frost on a fridge or freezer.
Re-qualification following Unplanned MaintenanceAlways consider re-qualification as part of an unplanned maintenance. Such an assessment should be based on the likelihood of the maintenance impacting either the control or uniformity of the environment. If in doubt, re-map.
Re-purpose or Change to ConditionStorage environments are generally able to operate at a range of conditions and it may be a business requirement to occasionally change these conditions to accommodate different studies. It cannot be guaranteed that condition accuracy and uniformity is the same at two different operating conditions, so this must be verified through mapping every time such a change is made.
Step 2 – Determine Your States of Mapping
Your next step is to determine how to set up the environment for mapping. It’s important the data obtained during mapping is representative of that environment during routine operation but also that extreme scenarios can be highlighted and prepared for. The main states of mapping to consider are:
EmptyMap the environment containing shelving only to assess the impact to conditions when storing low loads.
FullMap the environment containing a simulated load, representative of typically stored materials, to assess the impact to conditions when storing high loads.
In UseMap the environment without change to the current load to be indicative of the normal operating conditions. This state commonly applies when performing routine re-mapping.
In some environments, additional extreme scenarios may be simulated for mapping, these include open door, power loss and seasonal states.
Open DoorDuring access of storage environments through routine use, the internal conditions may be impacted. To help identify this impact and provide suitable precautions to be taken, an open-door assessment may be performed. This involves opening the door to the environment for pre-determined intervals, commonly representative of your typical access time during routine operation, and assessing the time taken for each location to deviate from tolerance as well as recovery time upon closure.
Power LossSimilarly, assessment may be made as to how long conditions are maintained if power supply is lost. This information can aid with risk assessment of such an eventuality during routine operation.
SeasonalSome storage environments may be impacted by external conditions. To determine this, seasonal mapping can be performed on a cold winter day and again on a hot summer day. This state of mapping is more commonly performed on environments of ambient, non-controlled conditions.
Step 3 – Pre-Assess Your Environment
A pre-assessment considers the size of the environment and its contents. Use yours to determine the number of loggers you need and their locations within the area to ensure an adequate representation of the environment.
Data loggers must be distributed evenly within the environment being mapped, keeping in mind any high-risk areas, to obtain a complete profile of the space. Each environment should be assessed to identify these high-risk areas where samples would routinely be located. Place an additional data logger in each of these locations:
- Adjacent to the internal monitoring probe of the environment.
- Adjacent to any feature or area at higher risk of environmental fluctuations e.g. heaters/coolers, humidifiers/dehumidifiers, access points, ventilation, windows etc.
- Outside the environment being mapped. This acts as a control and can be used to assess impact of the external environment on the internal conditions. Should the state be seasonal mapping, the logger should be positioned outdoors.
The number of data loggers required is dependent on the size of area being mapped and the number of high-risk areas identified. For a small, reach in unit, the minimum number advised would be nine; four top corners, four bottom corners and one central. As the size of the environment increases so does the number of loggers required to achieve representative distribution.
The final stage before you are ready to go is to determine your mapping duration and recording frequency. As standard, 24 hours is considered appropriate for each state of mapping (empty, full and in-use). Generally, this gives sufficient time to allow any operational cycles to occur. However, you need to know your equipment and how each of the components interact. Some cycles can be much longer in duration, in which case the environment should be mapped over a longer period. For a 24-hour mapping, a recording frequency of every 5 minutes provides sufficient data points without risk of fluctuations being missed.
Step 4 – Map!
Step 5 – Evaluate Your Data
When evaluating your data consider the following:
Have all locations met the criteria for that environment? The mean recorded values for each data logger provides the best representation of the conditions at that location over the mapping duration.
Do all locations remain in tolerance for the full mapping period? Absolute minimum and maximum values recorded at each location should be considered when determining an environment fit for purpose. A deviation on an absolute minimum or maximum recorded value may be justifiable if it is of minimal degree and short duration across the period; however, the impact of any such excursion should be assessed and documented.
Can a conditional pass be granted? If one location does not meet criteria, can this be taken out of use and clearly identified as a ‘DO NOT USE’ zone.
What is the impact to previously stored materials? In the event of a failure of a routine re-map, you must risk assess the storage that has gone before.
Can the conditions of the environment be improved? Even if all locations are in tolerance it may be possible to reduce the risk of future excursions by adjusting the controls or set-point. Look at the range or your data, is it skewed?
Once these 5 steps have been satisfactorily completed you are ready to determine the environment as ‘fit for purpose’ and can be confident that your stored materials are in good condition!