Does an RECD Need Internet Access to Operate?

It’s a question that comes up more and more as RECD controllers gain screens, data ports and, sometimes, cloud dashboards. An IT manager is asked to open a firewall port. A facility in a basement with no mobile signal wonders whether its device will still work. A security-conscious hospital or data centre wants to know whether a new emission control device adds another route for cyber attacks.

The short answer is no. A Retrofit Emission Control Device doesn’t need internet access to clean exhaust. The longer answer depends on what kind of RECD you have, what connectivity adds, and how much risk your site is willing to accept in exchange.

This guide separates what an RECD needs to work from what connectivity can add, explains the risks, compares connection options, and lists the questions to ask your supplier.

What an RECD Needs to Work

At its core, an RECD is a physical and chemical device in the exhaust path:

• A filter substrate traps particulate as exhaust flows through it
• A catalyst coating, where fitted, oxidises CO, hydrocarbons and part of the particulate, and may help burn trapped soot
• Regeneration clears trapped soot, either passively using exhaust heat, or actively using a heater or other assistance controlled locally

None of these processes involves the internet. Exhaust flows, particles are trapped, and the chemistry happens regardless of connectivity. See what is an RECD and how does it work.

Devices with active regeneration need a local controller, sensors and electrical power. Those are local requirements, not internet requirements. See RECD controller and heater power supply requirements.

Three Types of RECD, Three Answers

RECD type	Needs electricity?	Needs a local controller?	Needs internet to filter?
Passive (exhaust-heat regeneration, gauge only)	No (or only for optional sensors)	No	No
Controller-monitored (sensors, display, alarms)	Yes, for the controller	Yes, for monitoring	No
Active regeneration (heater or assisted)	Yes	Yes, for regeneration control	No
Any of the above with a cloud dashboard	As above	As above	No. Internet is only for remote viewing and alerts

If a supplier says a device can’t filter without an internet connection, ask for a clear explanation. That would be unusual and would make the device dependent on something outside your site’s control.

What Internet Connectivity Can Add

Connectivity is optional, but it isn’t pointless. It can offer real benefits:

Remote visibility

Facility managers, maintenance contractors and the RECD supplier can see ΔP, temperatures, regeneration status and alarms without visiting the site. That’s especially useful for:

• Unattended or remote sites, such as telecom towers and pumping stations. See RECD for telecom sites: remote unattended operation
• Organisations with many sites, which want one dashboard
• Sites without a Building Management System

Alerts to phones or email

Alarms can be pushed to the right people even if nobody is in the plant room. See how to design an RECD alarm response matrix for operators.

Long-term data storage

Cloud platforms can keep years of trend data, useful for tracking ageing, planning ash cleaning and supporting compliance records. See can RECD efficiency change between new and aged conditions.

Supplier support

With permission, the supplier can review data remotely before sending a technician, which can shorten fault diagnosis.

Software updates

Some controllers can receive firmware updates remotely. That’s convenient, but it’s also one of the riskiest functions (see below).

What Connectivity Can Cost You

Every connection to the internet is also a potential route in. For an RECD controller, the main risks are:

• Unauthorised access: someone outside the organisation viewing data, changing settings or disabling alarms
• A pivot point: a poorly secured device on the building network being used to reach other systems, such as the BMS, fire systems or corporate IT
• Tampered updates: malicious or faulty firmware pushed to the controller
• Dependence: if alarms only reach people through a cloud service, an internet outage or a supplier’s service problem can silently stop alerts
• Data ownership and privacy: operating data stored on third-party servers, possibly outside India, under terms you haven’t reviewed
• Ongoing cost: data plans, subscriptions and platform fees

For a single small DG set, these risks may be modest. For a hospital, data centre, airport or government building, they need proper assessment. Guidance on securing operational technology, such as the ISA/IEC 62443 series and the US NIST guide to operational technology security (SP 800-82), applies to RECD controllers as much as to any other building or industrial control device. In India, CERT-In publishes advisories and reporting requirements relevant to connected systems.

Connection Options, From Most Isolated to Most Connected

Option A: Fully local (no network)

The controller shows data on its own display and provides hardwired alarm contacts. Nothing leaves the DG room except a wire to an alarm panel.

• Security: highest
• Visibility: lowest; someone must visit the DG room
• Good for: small sites, high-security sites, sites where the BMS already covers the DG room via hardwired alarms

Option B: Local network only (BMS or SCADA)

The controller connects to the building’s BMS by Modbus RTU, or by Modbus TCP or BACnet on an isolated operational technology (OT) network. Data reaches the control room but not the internet. See integrating RECD monitoring with a building management system.

• Security: high, if the OT network is properly separated from IT and the internet
• Visibility: good on site
• Good for: most commercial and industrial buildings with a BMS

Option C: Outbound-only cellular gateway

A small gateway with its own mobile data connection reads the controller locally and sends data outward to a cloud dashboard. It accepts no incoming connections. It doesn’t connect to the building network at all.

• Security: moderate to good. It is separated from building networks, but the security of the gateway and cloud platform matters
• Visibility: good, from anywhere
• Good for: remote sites; sites that want supplier monitoring without touching corporate IT

Option D: Through the building’s internet connection

The controller or a gateway uses the site’s own internet connection, through the corporate firewall, to reach a cloud service.

• Security: depends heavily on network design and IT policy
• Visibility: good
• Good for: sites whose IT team approves and manages the connection

Option E: Inbound remote access (open ports, port forwarding)

The controller is made reachable from the internet so someone can log in to it directly.

• Security: lowest. Exposed control devices are routinely found and probed by automated scanners
• Recommendation: avoid. If remote access is needed, use a secure, managed method approved by your IT team, with strong authentication and logging

Which Option Suits Which Site?

Site type	Typical recommendation
Single small DG, no BMS	A (local) or C (cellular gateway) if remote alerts are wanted
Commercial building with BMS	B (local BMS), plus C only if the supplier needs data and IT agrees
Hospital, data centre, critical infrastructure	B, with any external connection reviewed under the site’s OT security policy
Multi-site portfolio (retail, telecom, banks)	C (outbound cellular gateways to a central dashboard)
Unattended remote site	C, with local hardwired alarms as backup
High-security government or defence site	A or B only, unless approved through formal security review

What Happens If the Connection Drops?

This is the most important design question if you do use connectivity. A well-designed system:

• Keeps filtering and regenerating normally, because the RECD and its local controller don’t depend on the connection
• Keeps local alarms working, through the controller display, hardwired contacts and the BMS
• Buffers data locally and uploads it when the connection returns (often called store-and-forward), so trends have no gaps
• Raises a “connection lost” alert to someone, after a sensible delay, so a silent outage doesn’t go unnoticed

Ask your supplier to demonstrate this. A system whose alarms only exist in the cloud fails exactly when you need it, for example during a regional outage when the DG is running and mobile networks are congested.

Connectivity also needs power during grid failures. See RECD monitoring during a power failure: what should stay available.

Worked Example: Three Sites, Three Choices

These examples are illustrative, but typical of decisions facilities make.

Site 1: A housing society with one 250 kVA DG set

The society has no BMS and a part-time maintenance contractor. The managing committee wants to know if the RECD develops a problem, but has no IT staff.

Choice: a local controller display, a hardwired common alarm to the security cabin, and an outbound-only cellular gateway sending alerts to the contractor and two committee members.

Why: the gateway is independent of residents’ home networks, needs no firewall changes, and gives remote alerts. If the mobile network fails, the security cabin alarm still works. See RECDs for housing societies: a purchase planning guide for RWAs.

Site 2: A hospital with four DG sets and a BACnet BMS

The hospital’s IT and biomedical teams have a strict policy on connected devices. The BMS is on an isolated OT network.

Choice: each RECD controller connects by Modbus to a gateway on the OT network, which presents points to the BMS. There’s no internet connection for the RECDs. The supplier receives monthly trend exports by email from the facility team. Remote access for troubleshooting is only allowed through the hospital’s approved, supervised remote-access process, case by case.

Why: monitoring is fully integrated into the hospital’s existing alarm workflow without adding a new external connection. See RECDs for hospitals and integrating RECD monitoring with a building management system.

Site 3: A telecom operator with 300 tower sites

Sites are unattended, spread across several states, and already have remote monitoring for batteries and DG sets.

Choice: RECD data is added to the existing site controller’s points, using the operator’s established and security-reviewed telemetry link to its network operations centre.

Why: reusing a managed, already-approved channel avoids adding 300 new connections, and alarms go to a team that already watches these sites around the clock. See RECD for telecom sites.

All three RECDs filter in exactly the same way. Only the monitoring design differs, to match each site’s risks and resources.

What a Good “Offline-First” Design Looks Like

Whatever connectivity you choose, design so the RECD and its local monitoring work fully without it. A practical checklist:

• Filtration and regeneration don’t depend on any network
• The controller has a local display showing key values and alarms
• At least one hardwired alarm output goes to a staffed location or panel
• The controller stores data locally for a useful period, such as weeks to months
• Settings are held in non-volatile memory and survive power and network loss
• Any gateway buffers data and forwards it when the connection returns
• Loss of connection itself raises an alert, after a sensible delay
• Monitoring equipment is powered from a supply that’s live while the DG runs

If a design meets every point, connectivity becomes a convenience rather than a dependency.

Keeping Records Without the Cloud

Some organisations worry that without a cloud platform they won’t have the records needed for compliance, warranty or reporting. Good records can be kept locally:

• Controller logs: download them periodically, for example monthly, with a laptop or USB, according to the supplier’s instructions
• BMS trends: export ΔP, back-pressure, temperatures and regeneration events from the BMS history
• Manual checks: keep a simple log of routine readings at the standard check condition. See why RECD test results may differ from day-to-day site readings
• Maintenance records: cleaning, repairs and alarm responses

Store these with the RECD’s certificate and test reports. Together they show that the device is monitored and maintained, which is what inspectors and auditors want to see. See the environmental compliance checklist for generator owners.

Questions to Ask Your RECD Supplier

About operation

1. Does the device filter and regenerate fully without any network connection?
2. Which functions, if any, depend on the cloud?
3. Do local alarms and the display work if the internet is down?

About connectivity design

4. What connection options are available: local only, Modbus/BMS, cellular gateway, site internet?
5. Is the cloud connection outbound only, or does it accept incoming connections?
6. Is data buffered locally during outages?

About security

7. How are devices authenticated to the cloud platform?
8. Is communication encrypted?
9. Can default passwords be changed, and are they unique per device?
10. How are firmware updates delivered and verified? Can we approve updates before they’re installed?
11. How are security vulnerabilities reported and fixed?

About data

12. Where is the data stored, and who owns it?
13. Who at the supplier can see our data, and why?
14. Can we export our data in a standard format?
15. What happens to our data if we end the service?

About cost and continuity

16. What are the ongoing costs (data plan, subscription)?
17. What happens if the supplier’s platform changes or is discontinued?

Include the answers you need in your purchase documents. See how to write a technical RFQ for an RECD project and RECD service response commitments.

Practical Security Basics for a Connected RECD

If you do connect your RECD monitoring:

• Change default passwords and use unique credentials
• Keep the controller off the corporate IT network. Use an isolated OT network or an independent cellular gateway
• Never expose the controller directly to the internet through port forwarding
• Allow outbound connections only where possible
• Restrict who can change settings, and log changes
• Approve firmware updates before installation, and keep a record
• Review access when staff or contractors change
• Include the device in your site’s asset register and security reviews

These are ordinary good practices for any connected building system. They apply just as much to emission control equipment.

Busting a Few Myths

“Without internet, nobody will know if the RECD fails.” Local alarms, a BMS connection and routine checks of ΔP and opacity can all catch problems without the internet. See why RECD test results may differ from day-to-day site readings.

“A cloud dashboard proves compliance.” A dashboard shows operating data, which is useful supporting evidence. Compliance with the CPCB requirement is based on certified devices and proper emission testing. See how to verify a CPCB-tested RECD on your DG set.

“Connected devices are automatically insecure.” Not if they are designed and installed carefully. Outbound-only, encrypted, well-managed connections can be reasonably secure. Poorly configured ones can’t.

“A maintenance-free RECD doesn’t need monitoring.” All RECDs benefit from monitoring, connected or not. See what a “maintenance-free RECD” claim actually means.

Related Reading

• Integrating RECD monitoring with a building management system
• How to design an RECD alarm response matrix for operators
• RECD Modbus data: units, scaling and register mapping explained
• RECD monitoring during a power failure: what should stay available?
• RECD maintenance guide

Frequently Asked Questions

Will my RECD stop working if the internet goes down?

No. Filtration and regeneration happen locally in the device and its controller. At most, you lose remote visibility until the connection returns. A well-designed system buffers data and keeps local alarms working.

Is a SIM-based gateway safer than connecting to our office network?

Often, yes, because it keeps the device completely separate from your building and corporate networks. Its security still depends on the gateway and cloud platform being properly designed and managed.

Can the RECD supplier change settings remotely?

Only if the system allows it and you permit it. Ask whether remote changes are possible, who can make them and how they’re logged. For many sites, read-only remote access is the safer choice.

Do I need IT approval to connect an RECD to the internet?

In most organisations, yes, if it uses the site’s network. Even with an independent cellular gateway, it’s good practice to inform IT and include the device in your asset and security records.

Our DG room has no mobile signal. Can we still get remote alerts?

Yes, in several ways. A hardwired alarm can be run to a location that is staffed or has signal, such as a security cabin or control room. The BMS can forward alarms through the building’s own systems. Or a cellular gateway can be placed outside the DG room, with an external antenna or a cable run back to the controller. Choose the option that fits your site’s security policy and cable routes.

Will a firmware update change how my RECD performs?

It shouldn’t change the filter’s physical performance, but it can change how the controller monitors, alarms or manages regeneration. Ask the supplier what each update changes, approve updates before they’re installed, and re-check alarm limits and BMS mappings afterwards. See RECD Modbus data: units, scaling and register mapping explained.

Does a cloud-connected RECD help with Pollution Control Board inspections?

It can help by providing trend data and alarm history, which show the device is monitored and maintained. Inspectors will still expect to see certification, test reports and maintenance records. See what happens during a Pollution Control Board inspection.

Connectivity Is a Choice, Not a Requirement

An RECD does its job in the exhaust, not in the cloud. Connectivity can make monitoring easier, as long as it’s designed so the device and its local alarms keep working when the connection doesn’t. Aceget supplies CPCB type-approved Retrofit Emission Control Devices for DG sets from 25 kVA to 2500 kVA. We can advise on monitoring options that suit your site’s security requirements. See our certifications, or contact our team.