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  • Do you offer discounts for bulk purchase?
    Yes we do. For larger instrument requirements for hire, service or purchasing we have a variety of pricing plans available. Please contact us to discuss and we would be happy to organise a formal quote for you.
  • Do you offer credit accounts?
    Yes! Contact our accounts team and we will happily consider a credit account.
  • What are your delivery times?
    Depending on stock levels, delivery times vary between 1-2 business days, and up to 8 weeks for less common items. Contact us for specific lead times.
  • Where can I get some additional technical support?
    We have a variety of resources available for you including our youtube channel and technical notes and datasheets on all our products. If you require immediate support call us on +44(0)1489 326031 or contact us during work hours on the web chat below.
  • What instruments can you calibrate?
    We are a fully authorised service centre for all our partners. We are also able to calibrate some other instruments so please do contact us with your requirements and we would be happy to assist or point you in the right direction.
  • Do you offer consultancy services?
    Unfortunately not, as many of our customers are themselves consultants. We provide instrumentation for monitoring and can provide best practice user training on said devices but this in no way replaces services provided by accredited consultants.
  • Can you train our staff?
    Yes as part of any instrument purchase we offer free of charge best practice user training outlining how to get the most out of your instrument and basic usage. We also have a variety of full training packages available and you can find more information about those on our training page.
  • Do you have ISO9001 Certification?
    Yes we are fully ISO9001 approved a copy of our certificate can be found below.
  • What's your shipping rate?
    Our standard rate to mainland UK is £25.00 for next day delivery Ex VAT. For international shipping we quote based on region, product value and weight.
  • Can we try before we buy?
    Yes, we offer a full hire fleet of our instruments and are able to offer a 2 week refund of hire fees against any purchase.
  • How much do you charge for calibration?
    You can find a copy of our full service price list below.
  • Do monitors come calibrated?
    Yes, all our instruments are calibrated by our service team prior to dispatch so you can be guaranteed of the maximum period between service visits and you get a working instrument every time.
  • What's the turnaround time on Calibration?
    Usually same day if there are no parts required and you have an account with Safety Monitors. If we receive the instrument in the morning it will be out in the afternoon.
  • How can I get a copy of my calibration certificate?
    We supply hard copies with instruments along with calibration tags however if you are unable to locate these for any reason please contact and we will get a copy sent out to you straight away.
  • Can you offer me an instrument whilst my unit is being serviced?
    Yes we have a full hire fleet we make available for our customers. This is usually available free of charge and comes as part of the service from Safety Monitors.
  • What's the process for booking a Service and/or calibration?
    We make it as easy as possible. Send your instrument to our head office address below a long with a copy of the Service and Calibration Form (or email this in advance) below to let us know anything specific you need us to look at and our team will be in contact as soon as we receive and inspect the instruments. Head Office: Safety Monitors Limited Unit 2 Church House Farm, Clewers Hill, Waltham Chase, Southampton SO32 2LN Tel: +44(0)1489 326031
  • What instruments are available for hire?
    Most of the instruments we supply can also be hired from Single Gas and 4 Gas Confined Space Monitors to Area Gas and Sound Level Meters we cover a full range of equipment. You can pre-book your hire online using our webshop or contact to confirm availability on 01489 326031. We are only able to offer hire within mainland UK as standard but may be able to accommodate you from one of our international offices so please contact us for continental requirements. If you wish to hire an instrument we will require a signed Hire Terms and Conditions form before we are able to proceed a copy of which can be found below we will at the point of confirmation send you this document via Docusign to Digitally Sign.
  • What is the minimum hire period?
    Our minimum hire period is usually 1 week however we are able to negotiate shorter periods if required.
  • Do you offer discounts on hire?
    Yes based on the duration or quantity of instruments we are able to offer up to 20% off for longer hire periods or larger quantities of instruments.
  • How quickly can I get hire equipment?
    Depending on the unit an availability we can get instruments out next day if order and paperwork is received before midday.
  • What VOCs can I measure with a PID?
    Photoionization Detectors (PIDs) respond to a broad range of chemicals including many volatile organic compounds ( VOCs) like alcohols and solvents, and some inorganic compounds, like ammonia and hydrogen sulfide. If the compound to be measured is also used to calibrate the PID, then the display will show directly the concentration of that compound. However, it is often difficult or costly to obtain a gas standard of the compound to be measured, and therefore a surrogate standard gas, typically isobutylene (IBE) is commonly used to calibrate the PID. This Tech/App Note lists the correction factors used to allow accurate measurement of hundreds of VOCs with different sensitivity using only isobutylene to calibrate. Isobutylene has the advantages that it is low cost, readily available, has low toxicity, and is not prone to adsorption losses on tubing connections. Correction Factor Definition With a PID calibrated to isobutylene and used to measure another compound, the reading is multiplied by the correction factor to obtain the true concentration: True Concentration = Reading x CF For example, if the unit is calibrated with IBE but used to measure acrolein with a CF of 3.9 and the reading is 10 ppm, then the true concentration of acrolein is 10 x 3.9 = 39 ppm. The mPower NEO series PID has about 200 correction factors in a built-in library. When the appropriate factor is called up, the unit displays the corrected reading directly as the true concentration of the compound. A compound with CF<1 is more sensitive than IBE while one with CF>1 is less sensitive than IBE. Unknown Compounds or Compound Mixtures If the nature of the VOC is unknown, then the PID cannot apply a proper factor or calculate a true concentration. In such cases the response is deemed to be an “Isobutylene-equivalent” response. For known compound mixtures (such as paint solvents), an overall CF for the mixture can be calculated as: CFmix = 1 / [X1/CF1 + X2/CF2 + Xn/CFn] PPM Where Xn and CFn are the mole fraction and correction factor for component n, respectively (In the case of a paint solvent the mole fractions can be obtained from the MSDS). However, if the mixture is variable over time, then it is again not possible to calculate an accurate CF or concentration. Matrix Gas Effects These CFs apply to measurements in air, unless noted. In most cases, matrix gas effects can be ignored, but for unusual situations corrections may be needed. • Oxygen at 100% reduces the VOC response by roughly 60% compared to pure nitrogen. Thus readings in pure N2 are about 20% higher than in air (78% N2/21% O2). • Hydrogen/Helium/Argon have little effect other than removing the oxygen quenching, and thus they cause about 20% increase in VOC response compared to air. • Methane/Propane cause significant quenching at concentrations above about 1% by volume. Therefore, PID measurements cannot be made in pure natural gas or liquid petroleum gas. In some cases, it is possible to dilute the fuel gas 100-fold to avoid the quenching and still have a measurable response to the minor component of interest. • Water Vapor. Humidity near 100% at room temperature can reduce the PID response to VOCs by about 40%. Below 50% RH corrections are generally not needed. Contact mPower for more details on how to make measurements in high- humidity environments. • Carbon Dioxide at 100% reduces the VOC response by about 20% compared to air. Correction Factor Definition The CFs in Table 1 were typically measured at 100 ppm or less and apply to concentration ranges from low ppb to a few thousand ppm. At higher concentrations, the factors are less accurate because curve-fitting is required to linearise the VOC response, and such curve fits are slightly different for each compound. For best accuracy, we recommend calibrating at concentrations in the general range of the expected VOC readings. Compound Formula and CAS No. In Table 1, the chemical formula together with the Chemical Abstracts Service Number (CAS No.) provide a means of uniquely identifying the compound. Compound Boiling Point Chemicals with low boiling points below about 100°C give a very fast response time of just a few seconds on the NEO series PIDs. Those with higher boiling points have increasingly slower response so that compounds boiling at 200°C may take up to a minute to obtain a steady reading. At even higher boiling points, accuracy begins to be impaired, as the compound vapors tend to be lost by deposition onto filters and inlet tubing and connections. For compounds like Therminol VP-1 with a b.p. of 257°C, the PID acts primarily as a leak detector without providing a precise concentration reading. A boiling point of 300°C is the upper limit for detectable compounds. TWA The Time-Weighted Average ( TWA) is a dose limit for worker exposure. This is included in the table to give an estimate of the toxicity of the compound and the concentration range that typically needs to be measured when the PID is used for industrial hygiene purposes. Full Correction Factor and Response Library for Neo
  • What's the difference between filtered and unfiltered LEL sensors?
    Filtered catalytic bead combustible gas sensors offers superior silicone poison resistance. The filter helps to prevent potentially damaging molecules from entering the sensor cavity and coming into contact with the heated refractory beads. There’s a tradeoff, however, that impacts certain applications for the use of portable safety gas detectors. The silicone resistant filter prohibits the diffusion of larger, more complex molecules. As a result, the filtered combustible gas sensor is suitable for the detection of the smaller molecule hydrocarbons, such as: methane, ethane, propane, butane, pentane, hexane, and hydrogen. It is not suitable for detecting: complex, large molecule hydrocarbons, alcohols, ketones, and esters due to the physical size of the molecules. If your application requires the detection of more complex hydrocarbons, or alcohols like ethanol and methanol, an unfiltered catalytic bead combustible sensor is recommended. But, be aware that even the unfiltered sensor has detection limitations as well. Most catalytic bead sensors are not suitable for the detection of combustible liquids having a flash point at or above 37.8°C (100°F). The catalytic bead combustible sensor is not ideal for monitoring combustible levels of complex hydrocarbon products like diesel fuel vapors and kerosene-based aviation fuel vapors with Flash Points typically of 37.8°C (100°F) and higher.
  • What's the difference between the Microclip XL and Microclip X3?
    Simply the X3 has a 3 year warranty and the XL a 2 year but to be slightly more thorough the XL uses a standard lead based Oxygen sensor which has a limited 2 year life where as the X3 uses an all new Oxygen sensor which can last up to 5 years. This can massively reduce ongoing maintenance costs for your fleet of gas monitors by at the very least halving the quantity of required sensor replacements over 5 years.
  • How do gas sensors work?
    Broadly speaking Safety Monitors offers the below gas sensing technologies: Electrochemical Non- Dispersive Infra Red (NDIR) Photo Ionisation Detectors (PID) Catalytic Bead/ Pellistor Colorimetric Gas Detection Tubes Although there are other sensors available for gas sensing on the market these are the technologies we primarily use in our detectors. Each of the above work differently and we would be happy to discuss in more detail or you can find more information on our YouTube channel.
  • What is a bump test?
    A bump test is a very quick performance retest of your instrument. You show the monitor a small amount of a known concentration of gas and check the unit is responding as you would expect. For example with a 4 gas monitor you would use a 4 gas mix of H2S, CO, LEL (usually Methane) and 18% Oxygen to check all the sensors are responding as you would expect. This isn't a replacement to a calibration but will confirm your instruments are responding as expected.
  • How frequently do I need to calibrate my gas monitors?
    Legally you should follow the manufacturers recommendation as dictated in the manual. This differs dependent on the manufacturer, instrument type and application but our general advice is as per below: Confined Space or Safety Monitor - 6 monthly Occupational Hygiene or Environmental Monitor (PID or similar) - Annually
  • Do I need a site visit?
    We would recommend a site visit for any fixed gas detection system. This is provided free of charge by Safety Monitors qualified personnel. For general instrument purchases there is no requirement but we are always happy to meet our customers and schedule some time to come to site, we may also be able to identify some solutions you may not have considered.
  • How can I ship calibration gas?
    Calibration gas should be treated as any other pressurised vessel and must be dealt with as hazardous goods.
  • What monitor should I chose for pre-entry testing?
    Dependent on the application you may require different gas sensors but we would always recommend a pumped instrument for pre-entry testing. This means you can keep the instrument in hand and using one of our sampling probes or retractable wands you can test the atmosphere in an area before entering.
  • What are VOCs?
    VOC is is an abbreviation for Volatile Organic Compound. Volatile - Gaseous at ambient conditions Organic - Containing Carbon Compound - Made of a mixture of elements They are found in a broad range of industries and atmospheres and have varying levels of toxicity. The limit values for said in the UK are based on a document called EH40 which is freely available for download from
  • What is a PID/ VOC Monitor?
    PID stands for Photo Ionisation Detector which is the technology we use for detection of Volatile Organic Compounds (VOCs). PID we liken to a low level LEL detector monitoring in Parts Per Million (PPM) or Parts Per Billion (PPB) ranges rather than is % Volume or % LEL levels. They are extremely sensitive monitors and although they are useful for detection of some substances Immediately Dangerous to Life or Health they tend to be more focused on low levels of substances which can cause health damage over the long term. They are used mainly in Occupational Hygiene and Environmental applications but also have some Safety applications.
  • What brands do you service?
    We are fully manufacturer approved for Honeywell, MSA, Crowcon, Watchgas at our Southampton Head Quarters and have a variety of other manufacturer capabilities at our European partners including but not limited to Industrial Scientific, Dråger and many more.
  • What sizes of gas canister do you supply?
    Our gas canisters are available in 34 Litre, 58 Litre and 116 Litre capacities.
  • What is fractional sizing?
    In term of dust and particulate monitoring the fractional sizes are the size of the particles smaller than which will be detected by the instrument. For example: PM10 - Monitors particle sizes below 10 microns PM4 - Below 4 Microns PM2.5 - Below 2.5 microns Anything below 10 microns is inhalable, anything smaller than 4 microns will make past the Thoracic region anything smaller than 2.5 microns is respirable.
  • What is gravimetric sampling?
    A gravimetric sample is collected using a constant flow sampling pump at a known volume in litres per minute. The collection media is weighed before and after sampling the difference is the amount of particulate.
  • What is the difference between a Sound Level Meter and a Noise Dosimeter?
    A sound level meter is usually used to monitor and area where as a noise dosimeter monitors personal exposure. A noise Dosimeter is usually only available with a Type 2 accuracy microphone where as Sound Level Meters are available as Type 1 or Type 2. You are also able to monitor more parameters with a SLM.
  • What is the difference between Type/Class 1 and Type/Class 2?
    A Type 1 Microphone has an accuracy of =/- 1dB where as a Type 2 is +/-2dB. A Class 1 Sound Level Meter has a noise floor (level below which you can not monitor) around 25dB where as a Class 2 instrument has a noise floor of 65dB.
  • What is an LAeq?
    An Leq is the average noise level over your monitoring period or a period of time. The A represents the weighting used. An A Weighting attenuates the response of the Sound Level Meter at Low and High Frequencies which are beyond the realms of human perception.
  • What is LCPk?
    A peak (highest) noise measurement over the period monitored with a C Weighting. A C sighting attenuates the noise signal at high frequencies but not at low frequencies taking into account pressure waves which although hey can not be "heard" can effect the human ear.
  • How often should my SLM be calibrated?
    A Sound Level Meter should be calibrated pre and post measurement using a calibrated reference source (acoustic calibrator). As long as your acoustic calibrator is calibrated every 12 months your Sound Level Meter can be returned every 24 months.
  • How do I monitor heat stress?
    The most accurate way is via monitoring core temperature of an individual using sensors within the persons orifices however this is often impractical so the next best is to use a WBGT Heat Stress monitor.
  • What is WBGT?
    WBGT is an abbreviation for Wet Bulb Globe Temperature. This reading in Celsius or Fahrenheit is not just a temperature but by using the Wet Bulb incorporates the effect of air movement, the high quality RH sensor will take into account humidity and the globe can take into account the radiant effect of light on the subject. This gives a much more accurate picture of the temperature experienced by an individual.
  • What's the difference between the QuestTemp QT30 series and QT40 series?
    QT30 Series uses a wet bulb which is filled using distilled water where as the QT40 series uses a high quality humidity sensor with proprietary algorithm to calculate the evaporative effect of water on an individual. In reality this means slightly less accurate measurements but as this removes the requirement to keep the wet bulb filled with water it improves usability of the instrument immeasurably particularly in environments where filling with distilled water can be challenging.
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