Indoor air quality

The ProCeas® NAV is designed for online monitoring of CO2, CO, Freon, H2S, H2, O2, Formaldehyde (…) in nuclear and conventional submarines. The ProCeas® NAV uses the OFCEAS method commercialized by Ap2e of France.

The OFCEAS system uses a high-finesse optical cavity to provide path lengths of tens of kilometres. Moreover the OFCEAS technology can also, in certain configurations, take advantage of broadband light sources to provide multi-component analysis, while offering improved sensitivity when compared with shorter path-length methods, such as Tunable Diode Laser absorption spectroscopy (TDLAS).

The ProCeas® NAV analyser has been designed to endure large temperature variations, high vibrations and englobes all criteria required by the military environment to assure long-term crew member health in a confined environment.

Some of the gases and measuring ranges available on the ProCeas® NAV are:

Carbon Monoxide CO: 0-1000 ppm – Lower Detection Limit: 1 ppm

Carbon Dioxyde CO2: 0-5% – Lower Detection Limit: 0.01 %

Hydrogen Sulfide H2S: 0-10 ppm – Lower Detection Limit: 0.1 ppm

Freon; R134a and R404: 0-1000 ppm – Lower Detection Limit: 2 ppm

Ethanol C3H6O 0-2000 ppm – Lower Detection Limit: 4 ppm

General characteristics

Response time < 10 sec

No Zero drift and no Span drift – No daily calibration required – No nitrogen, zero air, purge or other carrier gas.

Weight 15 to 20 kg

Dimensions 480 x 240 x 150 cm

As per the international OH&S regulations on Formaldehyde, Hutchinson, subsidiary of TOTAL, evaluated several technologies to implement continuous real-time monitoring of Formaldehyde at their Plant facilities.

The ProCeas® has been selected by Hutchinson as the technology the most suited to their monitoring needs in terms of response time, accuracy and flexibility around the integration within the mainstream of their installation.

Hutchinson uses the ProCeas® to measure various level of Formaldehyde in the air at 3 separated sampling locations: laboratory, offices & entrance hall.

ProCeas Key features

• Low detection level
• Complete pre-calibrated laser infra-red spectrometer
• Reduced response-time with Low pressure sampling system
• Suitable for a wide range of components in ambient air: NH3, O2, H2, H2S, HCFC, VOCs, (…)

Example of performances for the Formaldehyde

Measuring range: 0-10 ppm (up to 1%)

Lower detection limit: 1 ppb – (10 ppm at 1%)

Response time 2s

No Zero drift and no Span drift – No daily calibration required – No nitrogen, zero air, purge or other carrier gas.

Hazards of sterilant gases

Since sterilant gases are selected to destroy a wide range of biological life forms, any gas which is suitable for sterilisation will present a hazard to personnel exposed to it. The NIOSH Immediately Dangerous to Life and Health values (IDLH) for the three sterilant gases are 800 ppm, 75 ppm and 5 ppm for ethylene oxide, hydrogen peroxide and ozone respectively.

For comparison, the IDLH of cyanide gas (hydrogen cyanide) is 50 ppm. Thus exposure to even low levels of sterilant gas should not be treated casually and most facilities go to great lengths to adequately protect their employees. In addition sterilizers (as with any mechanical device) can and sometimes do fail and leaks have been reported. Continuous gas monitors are used as part of an overall safety program to provide a prompt alert to nearby workers in the event that there is a leak of the sterilant gas.

Monitoring Sterilant

The monitor alarms are typically set to warn if the concentrations exceed the OSHA permissible exposure limits (PELs), 1.0 ppm for ethylene oxide and 1.0 and 0.1 ppm for OH&S and ozone respectively. The PELs are calculated as 8 hour time weighted average values.

In addition to providing continuous monitoring, the better gas monitors include a computer based data acquisition system provides automatic data logging to assist with compliance with OSHA’s regulations and impending alarms that allow users to rectify problems before they become a hazard.

There are several technologies that are commonly used for the detection of sterilant gases, the main three being electrochemical, gas chromatography and metal oxide semiconductor. All three technologies are suitable for ethylene oxide, but only electrochemical sensors are used for hydrogen peroxide and ozone detection.

For ethylene oxide, metal oxide electrochemical sensors provide a low cost, long life detector offer very good sensitivity, fast alarm response times and small size. ChemDAQ gas monitor manufacturers mainly use electrochemical sensors for toxic gases because of their many advantages.

Electrochemical sensors have traditionally suffered from a cross sensitivity problems with other vapours (alcohols are especially troublesome in health care). Cross sensitivity results in false alarms, unnecessary evacuations and eventually a loss of confidence in the gas monitoring system.

ChemDAQ has developed a proprietary chemical filter that allows the ethylene oxide to pass through but removes most common interferent gases and vapours (including carbon monoxide, ethanol and IPA). The use of this filter allow the ethylene oxide to be detected with all the advantages that electrochemical sensors have to offer, but without the problems of cross sensitivity.