NTI boilers

The reports, as CPSC published them

1. No one hurt

   Made May 10, 2026 · , sent to the company May 14, 2026 · , published by CPSC May 29, 2026

   The product, in the report: an NTI TRX120 Series II boiler (Serial Number: 3314218 23 242360001826)

   The consumer was exposed to a hazardous buildup of carbon monoxide caused by incomplete combustion, following the failure of the product’s safety lockdown mechanism to engage.

   On 11/24/2025, an NTI TRX120 Series II boiler (Serial Number: 3314218 23 242360001826) was installed at the subject residence as part of the central HVAC heating system. During installation, the factory protective plastic sealing the combustion air inlet, which the manufacturer specifies must be cut open with a utility knife and removed prior to commissioning, was left intact by the installers.

   However, during winter operation, the boiler continued to fire for several weeks without triggering a safety shutdown. The prolonged unsafe operation remained undetected until outdoor temperatures dropped significantly, resulting in increased heating demand and sustained high-output operation of the boiler, when a persistent, high-frequency whistling sound originating from within the unit became pronounced and was subsequently identified as an operational anomaly, consistent with aeroacoustic resonance caused by high-velocity airflow forced through unintended leakage paths to compensate for the obstructed combustion air inlet, indicating severely restricted air intake. (Attachment #1)

   While the protective plastic has now been removed, and this report is not intended to seek assistance from the USCPSC in resolving a contractual dispute or obtaining financial restitution for installation-related issues, the incident raises concerns regarding the product itself, particularly its manufacturer-designed safety logic.

   Specifically, as a sealed-combustion, direct-vent high-efficiency gas boiler, the unit is designed to utilize its air pressure sensing logic to fail-safe against obstructed combustion air, regardless of the root cause, whether it be human error or external factors such as ice, snow, bird nests, or debris, by triggering a mandatory safety shutoff rather than allowing the unit to continue firing under oxygen-deficient conditions.

   This may indicate a potential design limitation in the units safety logic, allowing continued operation under incomplete combustion conditions, which can result in elevated carbon monoxide production and increased risk to occupant safety, particularly during winter when doors and windows are tightly closed to maintain indoor temperatures.

   Sustained incomplete combustion may also lead to increased formation of complex organic acids that are not typically present in significant concentrations during normal operation. This may diversify the acid profile of the condensate and increase its corrosive potential, contributing to accelerated degradation of internal and external components over time. (Attachment #2, #3)

   NTI TRX Series II once faced a nationwide recall by the USCPSC because similar models boiler doors could not be properly sealed, compromising the airtightness of this seal-combustion unit.

   https://www.cpsc.gov/Recalls/2025/NTI-Brand-Boilers-Recalled-Due-to-Fire-and-Carbon-Monoxide-CO-Poisoning-Hazards-and-Risk-of-Serious-Injury-or-Death-Made-by-NTI-Boilers

   While this specific NTI TRX Series II (120K BTU) is not included in prior recall actions, it utilizes the same sealed-combustion and direct-vent architecture as models previously subject to USCPSC recall notices involving airtightness safety concerns associated with fire and carbon monoxide hazards. Both designs are engineered to draw 100% of combustion air from the exterior via a sealed-venting system.

   If a unit is able to sustain combustion by drawing air through a sufficient number of unintended leakage paths, this may indicate compromised sealing integrity and a potential deviation from intended design performance, similar to conditions referenced in the recall notices for higher-BTU TRX models. If such air ingress is sufficient to sustain combustion under restricted intake conditions, it is reasonable to infer that, during periods of normal or incomplete combustion, pressure differentials within the system may, under certain conditions, permit flue gas migration through the same unintended leakage pathways, resulting in carbon monoxide exposure within the occupied living space.

   Alternatively, if the TRX120 units airtightness is assumed to meet applicable industry standards, the presence of unintended leakage paths within the chassis would not be expected to provide sufficient air ingress to sustain combustion or maintain a stable flame signal while the primary combustion air inlet is sealed. Under such conditions, the observed maintained flame signal and continued operation despite restricted primary air intake may indicate a limitation in the systems air pressure differential sensing and related safety control logic.

   As the boiler continuously fired over several consecutive weeks during winter before the issue was manually identified and addressed, the behavior is more consistent with a sustained operational anomaly rather than a transient or isolated event, suggesting it is unlikely to be the result of a single-point or incidental occurrence.

   In conclusion, there are two potential hypotheses for the units failure to initiate a safety lockout when the primary combustion air inlet was 100% obstructed:

   - Hypothesis I: Inherent Product Design Flaw. The internal safety logic may lack sufficient air pressure sensitivity to reliably detect sub-nominal pressure differentials across operating conditions. If the system cannot consistently identify restricted airflow, this may indicate a limitation in its ability to maintain a safe combustion environment under fault conditions. By potentially maintaining a flame signal despite an intake obstruction, the unit may continue operating under sub-stoichiometric combustion conditions, increasing the risk of elevated carbon monoxide production.

   - Hypothesis II: Installation-Induced System Compromise. Any possible installation errors or improper adjustments, including but not limited to modifications to the blower offset, recalibration of the air pressure switch, or alteration of the combustion fuel-air ratio, may have compromised the units intended safety lockout response, resulting in a failure to properly detect critical intake airflow restriction conditions.

   On January 20, 2026, a written statement from the installers was issued in communications involving the CEO of Home Depot, Mr. [REDACTED], stating that The installation was completed under a properly pulled mechanical permit and passed inspection and there is no indication that the unit is operating outside of required specifications or safety parameters.

   The compliance assurance suggests that the boilers continued operation under oxygen-starved conditions was not the result of manual intervention. While certain unrelated installation issues were identified and subsequently remediated, the core unit remained, and should have remained, in its original factory-unaltered condition, which is generally outside the scope of installation-related variables.

   Additionally, installers are typically not authorized to perform permanent modifications to safety logic prior to final system turnover to the customer, especially as an authorized service provider of Home Depot.

   Furthermore, the written statement indicates that any rare manufacturing variances are considered unlikely. The installers have reported, in the presence of Executive Office representatives, that there was no indication the unit was operating outside of required specifications or safety parameters, suggesting that adequate operational checks were performed as part of their installation and commissioning responsibilities to verify system integrity.

   This suggests that, if Hypothesis II is not supported by the available evidence, Hypothesis I: Inherent Product Design Flaw may warrant further technical evaluation of the systems safety control logic and failure detection mechanisms.

   This raises the possibility that, if a complete air intake obstruction in this extreme case failed to trigger a safety lockout, minor or partial obstructions such as insect nesting material or seasonal leaf buildup, or, particularly under extreme cold weather conditions where continuous boiler operation is required and snow and ice accumulation at exterior intake terminations can develop rapidly, may also fail to reliably initiate a safety shutdown in comparable residential installations, potentially increasing the risk of incomplete combustion and elevated carbon monoxide production.

   Under such conditions, without a safety lockout, the resulting pressure imbalance may also contribute to flue gas recirculation within the unit, further degrading combustion stability.

   Again, the incident raises concerns regarding the product itself, particularly its manufacturer-designed safety logic, rather than being related to financial or contractual matters, given that comparable sealed-combustion direct-vent boiler systems would generally be expected to trigger a safety lockout under similar conditions. This may warrant further evaluation by the USCPSC from a broader public safety perspective.

   Model

   TRX120 Series II

   Serial number

   331421823242360001826

   Bought from

   Home Depot

   Bought

   Nov 14, 2025, about then

   Where

   Silver Spring, Maryland: Home/Apartment/Condominium

   Who was involved

   Age 33, Male

   The reporter’s relation to them

   Self

   As this report names them

   Brand NTI, made or sold by Ariston Canada Inc.

   How badly, in CPSC’s words

   Incident, No Injury

CPSC’s disclaimer

Sources