How should the storage capacity of an explosion-proof video surveillance system be planned?

In explosive environments such as petrochemicals, coal mines, and hazardous chemical storage, explosion-proof video surveillance systems are the core facilities for ensuring production safety and preventing accident risks. Unlike ordinary monitoring systems, explosion-proof systems require complete storage of monitoring data while meeting explosion-proof level requirements. In the event of a leak, explosion, or other accident, the stored video data will become a key basis for accident tracing and responsibility determination. However, if the storage capacity planning is not reasonable, it may lead to premature data coverage, loss of critical information, or cost waste due to excessive configuration. This article provides a systematic planning solution from three dimensions: factors affecting storage capacity, calculation methods, and solution optimization, to help enterprises balance data storage needs and cost investment.

1、 Core factors affecting the storage capacity of explosion-proof video surveillance systems

The storage capacity of explosion-proof video surveillance systems is not a fixed value, and needs to be comprehensively considered based on the particularity of the application scenario, equipment parameters, and data retention requirements. Before planning, it is necessary to clarify the following four core influencing factors:

（1） Front end device parameters: Resolution and encoding format are the foundation

The resolution and encoding format of the front-end explosion-proof camera directly determine the daily storage capacity of a single camera and are the core basis for capacity calculation.

Resolution: Common resolutions for explosion-proof cameras include 1080P (2 million pixels), 4K (8 million pixels), and 5MP (5 million pixels). The higher the resolution, the larger the amount of data in a single frame, and the storage requirements also increase accordingly. For example, a 1080P camera has a single channel storage capacity of about 2-4GB per hour, while a 4K camera requires 8-12GB, which is about four times that of 1080P. Please note that some scenes in explosive environments (such as leak detection in tank areas) require high-definition image quality to capture details, and 4K resolution should be prioritized; For ordinary channel monitoring (such as main roads in the factory area), 1080P can meet the demand without excessively pursuing high resolution.

Encoding format: Currently, the mainstream encoding formats are H.265 (HEVC) and H.264. H.265 has a compression efficiency improvement of more than 50% compared to H.264- at the same 1080P resolution, H.264 encoding requires 3-4GB of storage per hour, while H.265 only requires 1.5-2GB. Explosion proof cameras should prioritize devices that support H.265+(enhanced version), and some high-end models also support the "dynamic bitrate" function: when the monitoring image is still (such as unmanned areas), the bitrate will be automatically reduced, and when the image is dynamic (such as vehicle traffic), the bitrate will be increased, which can further reduce storage usage by 30%, especially suitable for hazardous chemical warehouses and other scenes where the image is mostly static for most of the time.

（2） Data retention period: dual consideration of regulatory requirements and actual needs

The storage capacity is directly proportional to the data retention period, and the longer the period, the greater the required capacity. When planning, it is necessary to meet both industry regulatory requirements and the actual needs of the enterprise:

Mandatory regulatory requirements: Different industries have clear regulations on the retention period of monitoring data. For example, in the petrochemical industry, according to the Regulations on the Safety Management of Hazardous Chemicals, it is required to retain data for at least 30 days; According to the "Management Regulations for the Use of Coal Mine Safety Monitoring Systems and Testing Instruments" in underground coal mines, the retention period shall not be less than 7 days; For places involving major hazard sources (such as highly toxic chemical storage tank areas), some areas require retention for more than 90 days. Local new regulations should be followed to avoid compliance risks due to insufficient cycles.

Actual needs of enterprises: In addition to regulatory requirements, the actual needs of accident tracing also need to be considered. For example, if the explosion-proof monitoring of hazardous chemical transportation vehicles is only retained for 30 days, it may not be possible to trace abnormal transportation routes across months; For equipment inspection and monitoring within the factory area, if it is necessary to analyze the weekly operation pattern, the cycle can be set to 45 days, taking into account traceability requirements and cost control.

（3） Number of devices and coverage scenarios: on-demand configuration to avoid redundancy

The difference in the number and coverage of explosion-proof cameras will directly affect the total storage capacity. When planning, it is necessary to avoid a one size fits all approach and configure differently based on the importance of the scenario

Equipment quantity: Small gas stations may only require 4-6 explosion-proof cameras (covering refueling machines, tank areas, entrances and exits), while large petrochemical parks require hundreds of cameras (covering production equipment, pipe galleries, loading and unloading areas, emergency passages). The difference in quantity can result in a difference of tens of times in total capacity. It is necessary to first draw a monitoring point map, clarify the installation position and function of each camera, and avoid duplicate coverage (such as not installing more than 2 cameras of the same angle at the same time in the same tank area).

Scene difference: Some scenes require 24-hour uninterrupted recording (such as reaction kettle operation area, coal mine underground working face), while some scenes can be set with "motion detection recording" (such as factory walls, warehouses during non operation periods) - recording is only started when there is a moving target on the screen (such as personnel intrusion, object movement), and is not stored during non movement periods, which can reduce capacity requirements by more than 60%. It needs to be classified according to the risk level of the scene: high-risk scenes (such as explosion hazardous areas) are recorded 24 hours a day, while medium and low-risk scenes (such as the boundary between office and production areas) are recorded using motion detection.

（4） Storage redundancy: Dealing with equipment failures and data expansion

In explosive environments, storage devices may malfunction due to dust, vibration, and electromagnetic interference, and a certain amount of redundant capacity needs to be reserved to avoid data loss:

Equipment redundancy: When using "RAID array" storage, redundant capacity needs to be calculated. For example, RAID5 (a common solution) requires at least 3 hard drives, allowing 1 hard drive to fail, with redundant capacity of approximately 1/3 of the total capacity; If a safer RAID6 is used, allowing 2 hard drives to fail, the redundant capacity is approximately 2/5. Select the appropriate RAID level based on the number of storage devices. For small systems (up to 10 channels), RAID5 can be chosen, while for large systems (over 50 channels), RAID6 is recommended.

Data expansion redundancy: in actual operation, the code rate may exceed the theoretical value due to the complexity of the image (such as rainstorm, dust weather, which causes image noise to increase, and the code rate to increase by 20%), and 10% -15% of the idle capacity needs to be reserved to store system logs, backup files, and cope with the future demand for 1-2 channels of cameras, so as to avoid re expansion in the short term.

2、 Scientific calculation methods and examples of storage capacity

After mastering the influencing factors, the required storage capacity can be accurately determined through the three-step method of "single channel capacity calculation → total capacity calculation → redundancy correction" to avoid estimation bias.

（1） Three step calculation process

Step 1: Calculate the daily average storage capacity of a single camera

Formula: Single channel daily average capacity (GB)=bitrate (Mbps) × 3600 seconds × 24 hours ÷ 8 (byte conversion) ÷ 1024 (GB conversion)

Explanation: The bitrate needs to be determined based on the resolution and encoding format. Under H.265 encoding, the bitrate for 1080P cameras is usually 2-4Mbps, while for 4K cameras it is 8-12Mbps; If dynamic bitrate is enabled, take the average bitrate (e.g. 1080P dynamic bitrate averages 2.5Mbps).

Example: An explosion-proof camera with 1 channel 1080P, H.265 encoding, and dynamic bitrate (average 2.5Mbps), with a daily capacity of 2.5 × 3600 × 24 ÷ 8 ÷ 1024 ≈ 26.37GB.

Step 2: Calculate the total storage capacity (excluding redundancy)

Formula: Total capacity (TB)=Average daily capacity of a single channel (GB) × Number of cameras × Retention period (days) ÷ 1024

Example: A certain petrochemical storage tank area needs to install 10 explosion-proof cameras (all 1080P, H.265, dynamic bitrate 2.5Mbps), with data retention for 30 days, and a total capacity of=26.37 × 10 × 30 ÷ 1024 ≈ 7.71TB.

Step 3: Add redundancy correction (including RAID and data expansion)

Formula: Final required capacity (TB)=Total capacity (TB) ÷ (1- Redundancy ratio)

Explanation: The redundancy ratio is determined based on the RAID level and data expansion requirements, usually taking 30% (RAID5 redundancy is about 33%+data expansion is 10%, calculated as 30% overall); If it is RAID6, the redundancy ratio is set to 40%.

Example: The above storage tank area adopts RAID5 storage, with a redundancy ratio of 30%. The final required capacity is 7.71 ÷ (1-30%) ≈ 11.01TB. In actual selection, rounding up is required, and 12TB or 16TB storage devices should be selected (mainstream capacity should be preferred to avoid increased risk of failure caused by small capacity hard disk splicing).

3、 Optimization Strategy for Storage Solutions: Balancing Cost and Security

On the basis of meeting capacity requirements, storage solutions can be optimized through the following strategies to reduce costs while improving data security and adapting to the special requirements of explosive environments.

（1） Hierarchical storage: Separation of hot and cold data

Divide monitoring data into "hot data" (data from the past 3-7 days, requiring high-frequency retrieval for real-time viewing and anomaly tracing) and "cold data" (data from more than 7 days, requiring only archiving and minimal retrieval), and store them separately on different devices:

Hot data storage: using local high-performance storage (such as industrial grade SSD arrays), with fast read and write speeds, can quickly retrieve recent videos, suitable for real-time monitoring needs in explosive hazardous areas; SSDs have no mechanical components and have better anti vibration and anti dust performance than mechanical hard drives, making them more suitable for harsh environments in underground mines and chemical equipment areas.

Cold data storage: Low cost distributed storage (such as network attached storage NAS or cloud storage) is used to migrate data that has been stored for more than 7 days to cold storage devices, while only hot data is retained locally. For example, in a coal mine underground system, the local SSD stores 7-day hot data (with a capacity of approximately 10.98TB), and the cold data is migrated to NAS storage on the mine (with a 90 day cycle requiring only an additional storage of approximately 131.76TB). Compared to using only SSD storage, the cost can be reduced by more than 40%.

（2） Choose storage architecture on demand: combining local and cloud

Choose a suitable storage architecture based on the network conditions and security requirements of the scenario:

Local storage is preferred (recommended): In explosive environments, the network may be interrupted due to dust and electromagnetic interference. Local storage (such as explosion-proof hard disk video recorders and NVRs) can ensure that data is not lost when the network is disconnected, making it suitable for unstable network scenarios such as oil drilling platforms and underground coal mines. It is necessary to choose an NVR with an explosion-proof level that matches the site (such as Ex d IIB T4 Ga level for chemical areas and Ex d I Mb level for coal mines) to avoid safety accidents caused by insufficient explosion-proof levels.

Cloud storage as a supplement: For scenarios with stable networks (such as hazardous chemical warehouses and factory gates), "local+cloud" dual backup can be used: local storage meets real-time retrieval, while cloud storage serves as remote backup to prevent data loss caused by explosion or fire damage to local devices. When choosing a cloud service provider, it is necessary to confirm that it complies with the requirements of the Data Security Law, stores data on domestic servers, and supports access protocols for explosion-proof devices (such as ONVIF, GB/T 28181).

（3） Hardware selection: adapted to explosive environmental characteristics

The storage hardware must meet both explosion-proof requirements and storage performance to avoid data loss caused by hardware failures

Explosion proof level of storage equipment: Select equipment according to the classification of explosion hazardous areas on site. For Zone 0 (continuous presence of explosive mixtures), intrinsically safe (Ex ia) storage modules should be selected. For Zone 1 (occasional presence), explosion-proof (Ex d) modules should be selected. For Zone 2 (transient presence), increased safety (Ex e) modules can be selected; The hard drive should be an industrial grade hard drive (such as Western Digital Purple Surveillance hard drive), with a temperature tolerance range of -30 ℃ -65 ℃ and better anti vibration performance than consumer grade hard drives, suitable for low temperature and vibration environments underground in mines.

Interface and Scalability: The storage device needs to reserve sufficient SATA interfaces (for expanding hard drives) and network ports (supporting gigabit or ten gigabit networks to meet the data stream transmission of multiple 4K cameras); Some scenarios also require support for USB 3.0 interface for emergency backup data (such as quickly exporting critical videos after an accident).

4、 Daily maintenance and capacity management of storage systems

After planning the storage capacity, it is necessary to ensure the stable operation of the system through daily maintenance to avoid insufficient capacity or data damage caused by improper management.

（1） Regular capacity monitoring and early warning

Set capacity warning threshold: In the storage management software, set the capacity warning threshold to 80% (for example, when the total capacity reaches 12TB and the usage reaches 9.6TB, a warning will be triggered). The warning methods include local sound and light alarms, remote SMS/email notifications, to ensure that operation and maintenance personnel can promptly detect insufficient capacity issues.

Weekly capacity check: Regularly check the actual bitrate and storage usage of each camera. If the storage usage of a certain camera suddenly increases (such as bitrate rising from 2.5Mbps to 5Mbps), it is necessary to investigate whether it is due to equipment failure (such as lens stains causing increased image noise) or scene changes (such as adding frequently moving objects in the monitoring area), and adjust parameters in a timely manner (such as cleaning the lens, optimizing dynamic bitrate settings).

（2） Data backup and recovery testing

Regularly backup critical data: For monitoring data in areas with major hazard sources (such as reactor operation screens), perform off-site backup once a month (such as copying to a portable hard drive and storing in a secure area) to avoid data loss caused by damage to local storage devices.

Quarterly recovery testing: Randomly select 1-2 pieces of historical data (such as videos from 30 days ago) to test whether they can be played normally and check data integrity; If RAID storage is used, it is necessary to simulate a hard disk failure (such as unplugging one hard disk), test whether the RAID reconstruction function is normal, and ensure that data can be recovered in case of a failure.

With the application of AI intelligent analysis technology in explosion-proof monitoring (such as intelligent identification of leaks and flames, only storing abnormal images), the demand for storage capacity will be further reduced. Enterprises can achieve more efficient capacity management through a combination of "intelligent analysis+hierarchical storage", providing more reliable data support for the safety monitoring of explosive environments. If personalized storage solutions need to be developed for specific scenarios (such as underground coal mines or large petrochemical parks), detailed parameters can be provided to further optimize calculations and provide selection recommendations.

(III) Hardware maintenance and environmental control

Storage device cleaning: Clean the cooling vents and fans of storage devices monthly to remove dust (operation should be carried out with power off, using compressed air to blow away dust, avoiding wiping with water or wet cloth), to prevent dust accumulation from causing equipment overheating and affecting the lifespan of the hard drive. Storage devices located underground in coal mines need to have their explosion-proof enclosures checked for tightness every two weeks. If the sealing ring ages, it should be replaced promptly to prevent gas from entering the interior of the device.

Environmental temperature and humidity control: The operating temperature of storage devices should be controlled between 0℃ and 40℃, with humidity ranging from 30% to 80%. In high-temperature environments (such as petrochemical plant areas), cooling fans or air conditioners should be installed. In low-temperature environments (such as underground coal mines in northern China during winter), wide-temperature hard disks (-40℃ to 70℃) should be selected to avoid damage to the hard disks caused by abnormal temperature and humidity.

V. Conclusion

The planning of storage capacity for explosion-proof video surveillance systems is a comprehensive project involving "technology + compliance + cost". It requires precise calculations based on the monitoring needs of actual scenarios, while meeting the safety requirements of explosive environments and industry regulations, to avoid "compliance risks caused by insufficient capacity" or "cost waste due to over-provisioning".